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Thread: Hot-start issue with EFI - who has it, who doesn't

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    Default Hot-start issue with EFI - who has it, who doesn't

    Many people have reported having the typical 280Z EFI hot-start problem, where after ~10-20 minutes after shut-down (hot engine), the engine starts but runs very rough for what seems like 5 minutes but is actually about 30-40 seconds. Some people with EFI though, report that they don't have the problem (see #43 here - http://www.classiczcars.com/forums/f...tml#post452357). If we collect enough information, maybe a common solution (or non-cause) will appear. So far, headers and a straight fuel rail seem to be common to one engine that does not have the problem.

    If you have the hot-start issue, or if you don't, and have the time, please report here what you're running on your 280Z/ZX EFI system engine. For the sake of the passengers in these embarrassing situations, please.


    1. Me - 1976 280Z, stock EFI system, stock fuel rail, 1978 stock injectors, 1978 stock exhaust manifold and 1976 intake with heat shields intact. Consistent hot-start issues if the cooling fan (my own modification) is not turned on
    1976 280Z, with some minor modifications

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    Thanks for starting this, Zed!

    Mine is a 1978, stock EFI with new Standard FJ3 injectors with plastic insulators, stock exhaust manifold, all 1978 heat shields intact, and fuel rail covered in rubber hose. The engine is tight and runs very well with a CTS resistance mod. I USUALLY don't get hot restart issues. But SOMETIMES it does happen. Engine starts easily, but seems to be running on 2-3 cylinders. All cylinders fire up the first time I put the engine under load and stomp on the gas. Just revving the engine will work, but I have to do it for a while.

    FAIW, my hot restart problem was worse before I rebuilt my intake system. When I changed out my injectors, I retired the aluminum insulators and installed plastic. Perhaps that helped?
    Last edited by FastWoman; 03-19-2014 at 08:03 PM.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    Mine is a 1977, stock EFI, I also have the Standard FJ3 injectors (ebay $150), exhaust header (not wrapped), manifold heat shield (no pcv heat shield), stock fuel rail, FPR, etc. From Oct. to the end of Feb. CA puts additives in the fuel. I notice during this time of year I have an occasional "Hot start" issue but it only lasts for about 5 seconds. No other time have I experienced it. But then again the weather is usually beautiful year round here. Rarely gets above 80 deg. So I will assume that if I lived where the climate was warmer I would probably experience the worst case scenario. If the fan really does help then it sounds like the fuel is vaporizing in the fuel lines, injectors, or both. Maybe it has something to do with the type of fuel we all use now? This didn't happen when these cars were new or fairly new anyway. I didn't have this problem when I lived in Vegas for 17 years either so forget about what I said about warmer climates. Good thread! Need to think about this some more.

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    adding additional fuel during heat soak starts via cold start injector or main injectors won't work if there is only fuel vapor in the fuel rail. Perhaps a timer function for the fuel pump after engine is shut down to circulate fuel thats temperature activated. We all have various reasons
    for heat soak. Bad check valves, leaking injectors, higher percentage ethenol, vacuum leaks
    etc... Wouldn't it make sense to keep the fuel from vaporizing in the first place?

    I tried a manual switch to the fuel pump to prime the fuel rail before starting but it didn't help. Perhaps it was too difficult for the old worn out fuel pump to displace the vaporized gas? So maybe a couple 30 second or so cycles of the fuel pump immediately after its
    shut off will cool it down enough along with also some additional fuel enrichment would work.

    My band aid that works now 100% of the time is a zx injector fan on my 100% stock engine.
    Last edited by hr369; 03-20-2014 at 02:53 AM.

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    hr369, several of us have ruled out leak-down issues. My Z will hold fuel pressure just about forever, and it still has occasional hot start issues. I think our operating conclusion is that it's a design problem, hence Nissan's approaches of introducing hood vents in 1977 and an injector cooling fan with the ZX in 1979, and possibly even replacing the aluminum insulators with plastic. It might also have to do with ethanol gas, or winter gas formulations used in summer, which might vaporize at lower pressures.
    Last edited by FastWoman; 03-20-2014 at 06:35 AM.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    2 more things to add here. My pressure bleeds off about 1.5 hrs after shut down and I have the cowl induction hood on my Z, which I want to get rid of! So the heat has a large opening to escape.

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    Sarah,

    I just watched a video last night of an MIT professor discussing winter blends and they do of course flash over a lower pressure/temp. I hadn't thought of this with regards to hot start, but it's right inline with what rcb reported in post #3.

    Len
    77 280z - test vehicle
    HellFire L28 digital ECU replacement janitor.

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    Re-posted from another thread mentioned in post #1 here, thanks Zed Head, you're a REAL problem solver , I'm shooting in the dark.

    "I didn't mention that I have the ceramic coated header from MSA. That could be important as I've never had the hot start problem since the header and new injectors on a open fuel supply with the aluminium rail and the FPR out the rear barb to the return line to the tank. It recirculates but not on top of the intake manifold."

    As soon as I can find one I'll get one of those infrared thermometers you can point at something to get the degrees and get some readings while it's hot, then after it sits for 10 or so minutes.
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    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Hello, my name is Mike, and I have a hot restart problem :

    1977 280Z. Stock injectors. Stock Headers with MSA Twice Pipe exhaust. Car will run great, both in the cold and in very warm temperatures, but will have the hot restart issue regardless. I've noticed that the problem goes away if I rev the motor up to 2,000+ for a few seconds and then let it idle. I've tried revving it up to 1,600 and 1,800 multiple times, for much longer than a few seconds, and the problem would still be present. Could there be a reason for this?

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    To be clear, Swede, the stock configuration is with a cast iron exhaust manifold, not headers. If you have headers and hot-restart issues, then that would put a dent in the heat-soak theory.

    Where are you in the US? And is your hot restart problem a summertime problem, or is it year-round?
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    Don't forget interacting variables. Not enough data to draw a conclusion yet. The more stories, the better.

    CrazySwede, do you have heat shields over your headers? Siteunseen has his heat shields intact, as you can see in the pictures.


    Edit - also, we're really just working on about a twenty minute window where there's too much heat. Right on the edge. It could be some small thing that is enough to stay below the threshold. Who knows, if it's radiant heat that's the problem, ceramic-coated injectors might do the job.
    Last edited by Zed Head; 03-20-2014 at 11:43 AM.
    1976 280Z, with some minor modifications

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    Quote Originally Posted by TheCrazySwede View Post
    Hello, my name is Mike, and I have a hot restart problem :
    Haha! You've taken your first step towards recovery.

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    My 280Z 5/77 has the problem occasionally. Not enough to drive me crazy, not yet anyways.
    Its running a stock N47 exhaust, non webbed N47 inlet, JECS green injectors with standard fuel rail, ERG and the heat shield are still intacked and functioning.

    I don't think a ECU fix with solve the problem completly. Sarah's theory (in the other thread) makes sense to me. The ECU will attempt to fix a symptom and not the cause, which seems to be vapour down around the injector tip.
    Datsun seems to have attempted to fix the problem over the years
    1; By using heat shields, removing the webbing in the inlet manifold to reduce metal which stores heat and
    2; The later ZX had the fan blowing cool air from the other side of the engine over the inlet manifold to reduce the heat.

    I think Siteunseen's set-up with the fuel rail would help cure the problem. The single rail means less amount of fuel above the manifold and it would be refreshed faster. Its why people are covering the fuel manifold to protect it from heat.

    I wonder if a N42 head would improve the heat problem. The exhaust ports from the N47 and P79 have emmision liners which generate extra heat. The N42 head doesn't have them and may not generate so much heat. You would need the change the valve seats to steel and get the corresponding exhaust manifold. If anyone has this setup, it would be nice to hear their view on this combination.
    Its just a theory. Of course its not based on any research and I don't have any plans on buying a N42 head to test it out.

    Chas
    Chas
    5/77 280Z HLS30 403100 with some modifications
    Original colour: 305 Light Blue. The PO changed it to Red

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    Quote Originally Posted by FastWoman View Post
    To be clear, Swede, the stock configuration is with a cast iron exhaust manifold, not headers. If you have headers and hot-restart issues, then that would put a dent in the heat-soak theory.

    Where are you in the US? And is your hot restart problem a summertime problem, or is it year-round?
    Aye, you are correct. I'm running with the factory exhaust manifold. I live in Commiefornia (CA) and I've had this issue occurring since around October of last year. The issue might have been present prior to that, but because the car wasn't my daily driver, I never noticed it. It is my daily now, so I've come to realize this issue. The car will run great otherwise. Even under hot weather conditions, the car will run strong and idle perfectly. Let it sit for 15-20 min (having it sit for 5 min does nothing) and it will act as if it's running on 5 cylinders. Capt. O suggested that I check my fuel pressure, so I did, and it gets proper pressure constantly, and maintains higher pressure when the car has been turned off as it should.

    I spoke to a Nissan mechanic last week or so about the issue and he thinks it could have something to do with the ethanol in the fuel and the mixture in winter fuel. He said that a lot of his customers that otherwise had no issues with their cars start to come in around winter time for this exact problem. I live in San Jose, and there's a great Z Specialty shop nearby (Z Car Garage) that I hope might figure something out. They are pretty popular, so I have to wait for my appointment date...which is almost 3 months from now :/

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    Quote Originally Posted by TheCrazySwede View Post
    Hello, my name is Mike, and I have a hot restart problem :
    Hello Mike! How many Z mechanics does it take to screw in a spark plug? 1, he holds the plug in place and the world spins around him.

    Heard that a court ordered AA meeting but it was how many alcoholics does it take to screw in a light bulb.
    Keep coming back!
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Quote Originally Posted by siteunseen View Post
    Hello Mike! How many Z mechanics does it take to screw in a spark plug? 1, he holds the plug in place and the world spins around him.

    Heard that a court ordered AA meeting but it was how many alcoholics does it take to screw in a light bulb.
    Keep coming back!
    Haha, haven't heard that one before.
    I hope to get to the bottom of this whole issue....
    Were you able to "cure" the problem with your setup? I'm not as car-literate as most of you here, so you'll have to be patient with me. I'm no stranger to cars, I grew up taking part in motorsport and I still do, but I was always more interested being behind the wheel than under the hood.

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    Yes I was able to cure it but at a greater expense than a injector cooling fan from the ZXs. I did all of it while rebuilding my motor, you know the old "as long as I'm here I might as well go there too" adage. Getting rid of all the emission stuff and spaghetti pile of hoses that were there were my main goal, we don't have the inspections in good old Alabama. If you could find one of those fans that would be the easiest fix until you're ready to go a lot further, headers and a straight through fuel supply. I love what Zed Head said, "For the sake of the passengers in these embarrassing situations, please."
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Quote Originally Posted by siteunseen View Post
    Yes I was able to cure it but at a greater expense than a injector cooling fan from the ZXs. I did all of it while rebuilding my motor, you know the old "as long as I'm here I might as well go there too" adage. Getting rid of all the emission stuff and spaghetti pile of hoses that were there were my main goal, we don't have the inspections in good old Alabama. If you could find one of those fans that would be the easiest fix until you're ready to go a lot further, headers and a straight through fuel supply. I love what Zed Head said, "For the sake of the passengers in these embarrassing situations, please."
    I hear ya. Yeah, unfortunately, good ol' Commiefornia won't let us pass on by in our classic Z's...unless mine was 2 years older, in which it would do just fine. I've read about the ZX's cooling fan setup and how it has managed to relieve a lot of issues regarding heating issues with these older Z's, but I've also read cases that object with quite contrary results. I don't remember specific threads or posts, but I've seen a few Z owners who have tried the ZX's cooling and still faced the same problem. Could this possibly be because of variable factors taking part in the issue? I don't see how a ZX's cooling fan could cure a leaky injector, for example. Given that cooling is the sole issue, would a ZX cooling system be the solution?

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    here was bosch' solution to the problem on vw's years ago.
    A fuel accumulator to keep pressure in the system a little longer.


    https://www.partsplaceinc.com/catalo...gekits48.shtml

    There is a patent out there that combines a pressure release valve with
    an accumulator. its a good read. What i find interesting is this ---> "The pressure from the vaporized fuel, in turn, may push any liquid fuel remaining
    in the fuel lines back into the fuel tank" I hadn't noticed a rise in fuel
    pressure after turning off the engine. Has anyone else noticed this?

    It's possible that just an accumulator will fix the problem. Has anyone here
    tried one?

    Patent US7267108 - Fuel system pressure relief valve with integral accumulator - Google Patents

    It appears the optimal location for the accumulator is right next to the fuel pump.
    this is a mercedes setup.
    Click image for larger version. 

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    Last edited by hr369; 03-29-2014 at 03:37 AM.

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    HR369, yes, I've noticed that after shutoff, the fuel pressure will slowly rise from its normal operating pressure to a plateau at the FPR's bleed-off pressure. One can only presume fuel is bleeding off into the return line at that point. This could be confirmed, of course, by removing the return line and watching what comes out (and when).

    It's worth noting that I've observed this on a warm (but not blistering hot) day in the shade with the hood standing open. This is one reason I believe the problem is heat passing directly from the cylinder head to the injectors.

    The accumulator sounds interesting, but I would think it might create a performance changes. When the throttle is suddenly opened up, the intake manifold pressure rises (vacuum decreases), and then the fuel pressure must be dropped by the FPR to compensate. There would be a lag created by the accumulator, as more fuel would have to be bled off for the pressure to drop. And then as the throttle is closed, fuel pressure would have to increase accordingly. It would take time to fill the accumulator back up. I wonder if the accumulator is used in a constant pressure scenario (not regulated in relation to intake vacuum).
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    The only affect the accumulator has on fuel pressure while the pump is running, is that
    it keeps the pressure more steady because of the reservoir of fuel it has. The magic happens
    when the car is shut off and the spring and diaphram take over and supply residual fuel pressure.

    Fuel pressure coming into the fpr is "always" constant and its the regulators job to raise or lower pressure. with the addition of an accumulator, its job has not changed. the only difference now is that pressure supplied to the fpr is more stable.

    the accumulator is kind of like a surge tank to prevent starvation on the race track.
    in our stock cars heat soak is the "race track"

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    HR369, if you were to install a pressure gauge anywhere in the system from the outlet of the fuel pump, to the injectors, to the inlet of the FPR, you would find that the pressure jumps up and down right along with intake manifold pressure. The FPR bottles up a 36 psi pressure differential between the fuel rail and the interior of the intake manifold, but because engine vacuum jumps up and down, so must fuel pressure. Any attempt to stabilize fuel pressure (with respect to atmospheric pressure) is going to make the system less responsive.

    BTW, I mucked up my description of the fuel pressure compensation in my prior post. Throttle open -> vacuum drops -> fuel pressure increases (relative to atmospheric pressure). Throttle closed -> vacuum intensifies -> fuel pressure decreases (relative to atmospheric pressure).
    Last edited by FastWoman; 03-29-2014 at 06:52 PM.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    ok, so i'm a little confusticated here...

    if the accumulator "stores pressure" between the fuel pump and the rail, wouldn't a drop in pressure due to throttle opening/closing simply pull a little of the "stored" pressure, which would be continually replaced by the pump? i'm not sure how the accumulator would make the system any less responsive, as the pressure would always be there - either from the accumulator or the pump itself, right?
    '78 280z - Daily driver/work in progress...

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    I understand the benifits of an accumulator, but I thought they are used on static pressure systems. Wont an accumulator mess up the effectivness of the FPR, making it less responsive because of the extra volume. The orifice in the FPR is rated to the capacity of the fuel pump.
    Chas
    5/77 280Z HLS30 403100 with some modifications
    Original colour: 305 Light Blue. The PO changed it to Red

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    rossiz, that only works on carbureted cars.

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    Quote Originally Posted by rossiz View Post
    ok, so i'm a little confusticated here...

    if the accumulator "stores pressure" between the fuel pump and the rail, wouldn't a drop in pressure due to throttle opening/closing simply pull a little of the "stored" pressure, which would be continually replaced by the pump? i'm not sure how the accumulator would make the system any less responsive, as the pressure would always be there - either from the accumulator or the pump itself, right?
    Well, when the pressure NEEDS to drop, this is achieved by the FPR spilling fuel into the return line. If there's no accumulator, relatively little fuel needs to be spilled to drop the pressure. On the other hand, if you have an accumulator full of pressurized fuel, much of the volume of that accumulator must be spilled before the pressure can drop. More spillage into the return line takes more time, hence less responsiveness. And then when pressure must again be built, that's accomplished by the FPR blocking fuel flow to the return line. However, the pump no longer simply has to repressurize the line. Instead, it has to fill up an accumulator, which again takes time and decreases responsiveness. Not mentioned in all of this, an accumulator could increase the work load of the pump considerably, as the pump would have to keep re-filling it after every dumping.

    As I said, I can see an accumulator being useful in a constant pressure system, but the L-Jet system is NOT constant pressure.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    the volume of these bosch accumulators is pretty small. what would it take to fill one? 3 -5 seconds? if that indeed is a
    problem, they do make a very small accumulator. see the size
    difference. Big one is first picture.
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    if you search on volvo hot start problem there are lots of forums with the same problem. i do believe many of the 70's and 80's volvo's use the same fuel pump check valve. I do
    believe thats part of the problem. Its too weak and allows
    bleed back when pressure rises after shutdown. Perhaps a
    different-better higher pressure check valve?




    The jeep cherokee guys have the same issues and they have resorted to the hood vents and injector fans too. they even
    had a recall because injector #3 was throwing a code. the
    band aid was a injector shield for #3 but didn't work very
    well. they use this fan timer if anyone is interested

    ELK-960 - ELK Delay Timer





    im wondering if there is any difference between the z and zx exhaust manifolds other than the additional o2 sensor. perhaps nissan made a beefier exhaust manifold that reduces
    heat soak?
    Last edited by hr369; 03-30-2014 at 04:35 PM.

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    HR369, those are interesting looking accumulators -- different from what I was understanding! They appear to have a vacuum fitting on the back end. Mentally reverse-engineering the things, if I'm understanding right, the pressure of the accumulator would rapidly track changes in the manifold vacuum, essentially maintaining constant pressure across the injector. In that case (with the vacuum fitting), that WOULD work. Furthermore, this accumulator design would raise the fuel rail pressure to 36 psi immediately upon engine shut-down, rather than the typical running pressure of 29 psi. This would help prevent vaporization.

    Are these mounted on the fuel pump assembly, with vacuum lines running that entire distance from the intake manifold, or are they mounted in a cooler part of the engine compartment, where a shorter run of vacuum line would be required? I'm wondering whether a part like this could be mounted in the vicinity of the fuel filter.

    If we're right about hot injectors flashing fuel that flows into them, this accumulator idea would not be a panacea, but it might help. It's interesting the Jeep folks have the same problem. Do the Jeeps have these accumulators?

    There shouldn't be any issue with weakness in the check valve. These valves fail through wear. If you've replaced yours and are still having your pressure leak down, you probably have an issue elsewhere -- FPR, injector, cold start injector. FAIW, I'm running the same Volvo check valve, along with new injectors, and my system holds pressure almost indefinitely. So there's no design issue with the check valve not being strong enough.

    Others have suggested the more massive exhaust manifold, relative to headers, would hold and radiate more heat, and I suspect there's merit to that thought. I suspect beefier manifolds would only aggravate the problem. Perhaps someone will will pipe in and say, "I had hot restart issues until I replaced my manifold with headers."

    FAIW, there was an evolution of manifold design over the years. In '75/'76, the intake manifold had no webbing and would allow free airflow from the exhaust manifold, up around the intake runners. In '77/'78, there was webbing between the intake runners and heat shielding around the exhaust manifold -- both between the exhaust and intake, and surrounding the exhaust. Then of course they went with the fan in '79.
    My last three sports cars while I still owned all three:

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    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    My 75 had the problem last summer time(when it was running right) it has a 79 block with a N42 head, new injectors, 79 fuel rail, new FPR, stock 75 exhaust manifold and heat shields. Did not have it this winter before I started having some issues with timing and fuel. My check valve is toast, holds pressure for maybe a minute. Don't know if this adds to the discussion, but there it is, I am convinced it only occurs with higher atmospheric temps, at least at it seems that way up here in the thin air.
    75 280Z almost done
    49 Chevy 3100 p/u next project
    96 Dodge 2500 4X4 tows my 5th wheel

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    Thanks for posting, they all count. So far, only one person with headers and EFI has posted, siteunseen, and he is the only one who doesn't have the problem. Wish we had more EFI and header people who would chime in.


    On the accumulator patent - That's a good find. The same reasoning was probably used by Nissan to develop the five second timer relay on the fuel pump circuit. It night be a typical covering-the-bases patent though. Filed in 2005, published in 2007, but no data on actual engine restart effects, just some pressure-time curves. With an FPR on one side and a big reservoir of fuel on the other, the net effect is to use fuel as a cooling agent. Hot fuel gets pushed through the FPR, back to the tank, and is replaced by new cool fuel from the accumulator. Interesting that they called out the 10% ethanol blend.

    Thanks for the link, the other citations in the patent will be some good rainy day reading.
    1976 280Z, with some minor modifications

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    Quote Originally Posted by mjr45 View Post
    My 75 had the problem last summer time(when it was running right) it has a 79 block with a N42 head, new injectors, 79 fuel rail, new FPR, stock 75 exhaust manifold and heat shields. Did not have it this winter before I started having some issues with timing and fuel. My check valve is toast, holds pressure for maybe a minute.
    Captain Obvious started a thread on alternative check vavles to solve the same problem you are having.
    http://www.classiczcars.com/forums/f...ernatives.html

    Which inlet manifold are you running; webbed or open?
    Chas
    5/77 280Z HLS30 403100 with some modifications
    Original colour: 305 Light Blue. The PO changed it to Red

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    1976, stock exhaust manifold, catalytic converter, heat shield, 1979 fuel rail and injector fan (with eBay time relay circuit set for 12 minutes), new fuel pump, FPR, ignition timing 15*, inline resistance pod.

    Previously I had heat soak issues, esp here in Bako town in the summer. After installing the 79 injector rail fan with a timer relay, there are no more incidents.
    - 1976 280Z
    - 1967 Camaro RS

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    Euro, I just read the thread on the check valve and will definitely be doing that, my intake is the open type. I'll also be changing the fuel rail to a single aluminum rail as I believe there is a very tiny almost microscopic leak right at where my #1 line comes off, I always find some burnt brown looking crud on the heat shield after running, but never see any fuel leaking. Oh well, another mystery for me to follow.
    75 280Z almost done
    49 Chevy 3100 p/u next project
    96 Dodge 2500 4X4 tows my 5th wheel

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    Quote Originally Posted by hr369 View Post
    They use this fan timer if anyone is interested ELK-960 - ELK Delay Timer
    Thanks for posting the link to the timer! This is great! I am planning to install with a ZX Fan.
    Andrew (ZCurves)
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    fastwoman - vw's that i've looked at have the accumulator located next to the fuel pump. Thats not to say other cars
    might have them far away from the fuel pump. But this is how
    bosch designed the system for vw's.



    good question on the cherokee using accumulators. i googled
    cherokee fuel accumulator and did not turn up any and the
    cherokee forums don't mention them.


    a vacuum line going from front to back would a pain and you might need a vacuum tank reservoir to keep a stable vacuum.
    i guess you could use the a/c hvac bottle in the engine compartment.


    the deloreans have the accumulator about 7' from the rear and it appears to be located away from the fuel pump.
    but... everyone knows how crappy that car performed.

    Fuel Accumulator Removal and Installation


    check valve alternatives -
    I ran across this high flow bosch check valve for the Bosch
    044 fuel pump it threads right into the fuel pump and uses AN style fittings. Bosch 044's are around 100 bucks new.



    Bosch 044 High Flow Check Valve, -6AN outlet [BFP-CV6] - $50.00 : Jay Racing
    Last edited by hr369; 04-03-2014 at 04:49 PM.

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    Default ZedHead maybe onto something...

    The people at Nissan realized the big 'ole exhaust manifold wasn't too good an idea. This is stock on a '82 ZX. A whole lot less heat holding cast iron!

    Oh yeah. I've got a ZX fuel injector fan somebody can have. The twice pipes that go over the valve cover is missing, fan and bracket only. Free, if someone wants to pay shipping. It works off my battery charger.
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    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    today i had what i think was a hot-start episode:

    warm, sunny afternoon, car up to full operating temp, went into the grocery store for about 20 minutes, came out and the car would not start at all - nothing, not even a pop after much cranking. i pulled the solenoid wire off the starter and turned the key to start to run the fuel pump, trying to circulate some fresh fuel around the rail - could hear it going and saw my pressure gauge blip up a little while the pump ran, but still no starting even after a few tries at this. maybe priming doesn't work because the fuel just runs around the rail and recirculates, without actually going down the short 90 degree hose runs to the injectors. took out a couple plugs and they were bone dry.

    let it sit for 5-10 min with the hood up, and then it started - ran rough for a moment until i reved it up above 2k and then it was as if nothing had ever happened.

    so i'm thinking - what if i set up a momentary push button switch to fire the cold start valve, even though the engine is hot? it's pretty far away from the block, so maybe it would be cool enough to provide enough fuel to get things started? i don't know how injectors work, but i thought they opened up when they received a pulse of power - if this is the case, wouldn't it just take a few cranks to pull some air/fuel in?

    i'm really not digging the feeling that it's just pot-luck whether my car will start when i come out of the store. especially since i had just gotten the car washed and it was looking SOOO nice, attracting admiring glances, then (sigh) hood up, fettling in the parking lot, hoping i could get home before the ice cream melted...
    '78 280z - Daily driver/work in progress...

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    I wonder if its sticking injectors. They are after all just a coil activating to pull on a magnet to open the neddle. The temperature could tighten the tolerances when they sit in high temerature and sieze shut until they cool off. Worn surfaces on the needle and the injector housing could grap easily and cause this problem.
    Vapour lock with 36psi, cranking the engine and even flushing cool fuel past the injectors seems unlikly, but I do mean seems.
    Manually pulsing the cold start injector could be a way around this.
    Chas
    Chas
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    Original colour: 305 Light Blue. The PO changed it to Red

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    Running the fuel pump will cool the "trumpet," and the legs leading to the injectors might also fill with fuel, but the injectors will still be hot. Actuating the cold start valve wouldn't cool anything down, any more than running the pump (which would do much more good), but it might spray enough fuel to run the motor. That would be a very fiddly way to start the motor, but it might work.

    Rossiz, for the sake of this thread... Yes, you indeed had a hot restart issue. What is the configuration of your engine?
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    After lurking on this Thread and suffering from these symptoms (Stock 78 setup), I am changing out the Injector Insulators to the plastic style and adding the ZX injector fan. I feel that with all of the heat shields in place that this might make the most difference. It is going to be a HOT summer here in Houston.
    Andrew (ZCurves)
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    yesterday i decided to do a little experiment. i detached my fuel rail leaving the injectors still attached to the rail. i then turned on the fuel pump and used a 9v battery to turn on and
    the injectors one by one. i thought i would have had at least one leaking injector. not even one little dribble could be seen. i also checked the cold start valve for a leak.


    i then pulled the injectors off the rail and soaked them in an ultrasonic bath of solvent.
    ran solvent both directions thru the injectors. its been 10+ years since i replaced these
    injectors so they were due for a good cleaning anyways.

    car ran more smoothly at idle but the real test will be when i go for a long drive
    and try to restart.

    btw i have the plastic injector insulators and a new check valve.

    the 280z exhaust manifold looks quite a bit more meaty than the zx manifold.
    perhaps a zx manifold would help the heat soak problem. does anyone in a 280z run
    a zx exhaust manifold?

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    Last edited by hr369; 04-10-2014 at 02:51 PM.

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    Quote Originally Posted by FastWoman View Post
    Actuating the cold start valve wouldn't cool anything down, any more than running the pump (which would do much more good), but it might spray enough fuel to run the motor.
    my point exactly: get some fuel in to start the engine and draw the vapor from behind the injectors.
    yes - it would be fiddly, but maybe it could be controlled more effectively by the HellFire? just a thought from a non EFI guy...


    Quote Originally Posted by FastWoman View Post
    Rossiz, for the sake of this thread... Yes, you indeed had a hot restart issue. What is the configuration of your engine?
    1978 280z - stock i/e manifolds, exhaust, fuel rail, heat shields, original injectors (i think)

    recent new parts (in last 6 months):
    - entire cold start system (thermotime sensor + connector, injector, AAR + hoses, connector)
    - PCV valve + hoses
    - FPR + hoses
    - AFM boot/hoses/connectors
    - all injector connectors (including cold start)
    - fuel pump check valve (rebuilt)
    - plugs, distributor cap, wires
    - water temp sensor + connector
    - thermostat
    - all fuel lines in the engine bay
    - most vacuum lines in the engine bay (vacuum currently measures 19 at idle)

    PO replaced parts/service (have receipts):
    - AFM (sept 2013)
    - ECU (1995)
    - injectors cleaned (2006)
    - fuel filter (2006)

    modifications:
    - K&N filter + cold air intake
    - EGR system removed and both manifold connections blanked-off
    - fuel pressure gauge installed between fuel filter and rail (reads constant 35psi)
    - fuel filter between tank & pump

    i've included some pics of the engine bay and one of the injectors - maybe you all can tell if they are original and if they are the "plastic insulator" kind (looks plastic to me)Click image for larger version. 

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    '78 280z - Daily driver/work in progress...

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    Quote Originally Posted by rossiz View Post
    - fuel pressure gauge installed between fuel filter and rail (reads constant 35psi)

    i've included some pics of the engine bay and one of the injectors - maybe you all can tell if they are original and if they are the "plastic insulator" kind (looks plastic to me)
    The fuel presuure seem a bit high. Normally maximum pressure is 36psi, but thats only under full throttle/ high load conditions when the vacuum is very low. At idle is should be under 30 psi. Does it change when you disconnect the vacuum from the FPR?

    The injectors don't look like OEM to me. OEM were green (JECS) and white (DKC).
    Chas
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    5/77 280Z HLS30 403100 with some modifications
    Original colour: 305 Light Blue. The PO changed it to Red

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    If you blow up the injector picture you'll see the typical A46(I think) - 00000 number of the stock Nippon Denso or Denso injectors. They look like they were probably green when new. Pretty dirty now.

    Those are the older style two part insulators, with the aluminum upper half. Hard to tell if they are better or worse for heat absorption. There's an air gap in the middle which might let them transfer heat faster, but the metal piece might hold more heat. Nissan might have changed just because it's cheaper to make a one piece plastic insulator than a two-piece.

    And that 35 psi constant is an unknown. Kind of odd, as EuroDat noted.

    To hr369 - I picked up a ZX manifold, more just to have a complete ZX engine package than for the heat-soak problem, but have realized that you need a longer head pipe to fit the shorter manifold. You'd have to do some exhaust work, it won't swap straight in.


    Back to Post #37 though, I'm not sure that's the typical heat-soak problem. It doesn't usually wipe out all of the injectors, just a few. The engine starts but runs bad. Yours didn't start all. That seems more electronic or electrical. Then when it did start you said it ran rough for a moment. Heat-soak running seems like eternity although it's only 20-30 seconds. But, if you do have it, it will come back, and you'll get familiar.
    1976 280Z, with some minor modifications

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    Default Z Curves ZX fan

    Here's a picture of it, I never can get one on a PM.
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    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Thanks! Thats the ticket! PM Sent.
    Andrew (ZCurves)
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    Quote Originally Posted by rossiz View Post
    i've included some pics of the engine bay and one of the injectors - maybe you all can tell if they are original and if they are the "plastic insulator" kind (looks plastic to me)Click image for larger version. 

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    Hello, It looks like the injectors in your pic are the OEM. The aluminum ring is actually clamps the injector into the manifold. BUT the aluminum transfers the heat more effectively to the metal injector body. Sarah(Fastwoman) had pointed this out earlier in the thread. Since I had to replace a dead injector anyway, I bought new Injector o-ring seals AND the plastic Fuel Injector mounts from Advanced Auto Parts. Below are the part numbers/prices...

    BWD/Intermotor Fuel Injector Seal Kit Part #28412 $6.49ea (You will need six).
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    Beck/Arnley Fuel Injector O-Ring Kit Part #158-0022 $3.29ea (You only need TWO - 4 in each package).
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    These changes may only make a minute difference - but it is cheap and worth a try. I will keep every posted as to my findings..
    Last edited by ZCurves; 04-11-2014 at 09:15 AM.
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    Here are some photo's of my injectors in the car and an old set on the bench. The ones in the car now are remanufactured and could be from a ZX.

    The originals were JECS Made in japan. The text on the back "1148" and "1701B". Its not on the set in the car. The set in the car have "086" and "0 280 150 116".
    I think they might be production numbers.

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    Chas
    Chas
    5/77 280Z HLS30 403100 with some modifications
    Original colour: 305 Light Blue. The PO changed it to Red

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    0 280 150 116 is the Bosch part number. I ran a set of those for a while. They seem to be the design that Nissan modeled their injectors on. They have a more vaporous injection pattern than the Nissan injectors, not that it seems to matter to performance.

    In your third picture isn't that an A46 - 00? I've not seen any over here that have JECS molded in to them, although I have seen a few ECU's and AFM's with JECS labels. I think that Nippon Denso was making most of these kinds of products for everybody in Japan back in the 70's. I've wondered if the JECS label goes on replacement parts or factory production parts.
    1976 280Z, with some minor modifications

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    Quote Originally Posted by Zed Head View Post
    0 280 150 116 is the Bosch part number. I ran a set of those for a while. They seem to be the design that Nissan modeled their injectors on. They have a more vaporous injection pattern than the Nissan injectors, not that it seems to matter to performance.

    In your third picture isn't that an A46 - 00? I've not seen any over here that have JECS molded in to them, although I have seen a few ECU's and AFM's with JECS labels. I think that Nippon Denso was making most of these kinds of products for everybody in Japan back in the 70's. I've wondered if the JECS label goes on replacement parts or factory production parts.
    I knew the injectors in the car were not original 280Z, but I didn't know they were Bosch.

    The A46-00 is correct. I managed to take a photo of the only one with unreadable text. I don't know the history of the JECS injectors, only that I replaced them with the remanufactured "bosch" injectors.
    Maybe the bosch came originally out of a Alfa romeo GTV6, BMW E12 or something similar? They used the Bosch injectors and Im told they are a bolt-in replacement.
    Chas
    Chas
    5/77 280Z HLS30 403100 with some modifications
    Original colour: 305 Light Blue. The PO changed it to Red

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    The 116 injectors seem to be the common replacement from back when people knew how to work on these engines. There must be a list or document out there that the mechanics had. FastWoman said that she had a set on 1975 car in the past, and I've seen them on several salvage yard cars. I actually picked up a full set from a salvage yard from a ZX. They worked great for about a year until one sprung a leak at the pintle. I'm 99% sure that 105 - 116 are the same injector except for hose length, based on the flow data that's out on the interweb. I keep my eyes open so that I can get one more to replace the leaker. They're used on VW Super Beetles with fuel injection, a few old Volvos, some BMW's and some Fiats. In case my experiment with 90's era injectors doesn't work.
    Last edited by Zed Head; 04-11-2014 at 12:05 PM.
    1976 280Z, with some minor modifications

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    this is what jeep did to prevent heat soak. notice the insulation is only in
    the center of the manifold. the zx injector fan also points to the center
    injectors.


    Click image for larger version. 

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    Injector heat shield - Jeep Wrangler Forum

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    megasquirt owners also deal with heat soak. someone suggested that the heat affects the copper windings inside the injector and reduces its pulse.


    for megasquirt owners there are no options? they do have MAT air density correction but it doesn't seem to help the
    problem much. would increasing pulse width during hot startups help solve the problem?



    will len's hellfire be able to compensate using software?

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    M54 Megasquirt 3: Fuel Injector Heat soak
    Last edited by hr369; 04-13-2014 at 06:19 PM.

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    I've owned ZX's since 1979. I've never experienced the problem described. I live in Georgia where 100+ days are common.
    Mine: 1979 280ZX 2+2 bone stock
    1979 280ZXR with mega-squirt, header, cold air intake, 60mm TB, JSK fuel rail, electric fans
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    Life is not a journey to the grave with the intention of arriving safely in a pretty & well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming--"WOW, what a ride!!!"


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    Quote Originally Posted by Zed Head View Post
    ...I'm not sure that's the typical heat-soak problem. It doesn't usually wipe out all of the injectors, just a few. The engine starts but runs bad. Yours didn't start all. That seems more electronic or electrical. Then when it did start you said it ran rough for a moment. Heat-soak running seems like eternity although it's only 20-30 seconds. But, if you do have it, it will come back, and you'll get familiar.

    ok, been away for the weekend so couldn't post about the "friday fiasco" until now...

    family trip involving a ferry (read as: can't be late) and i run a few errands for work, the day is sunny and 60's, last stop at an office for 20 min. while the z sits out in the sun. i come out and it does the typical dance: tiny "almost start" and immediate die, then NOTHING - no amount of cranking even gets a pop. i pop the hood and let it sit for a full 20 min. and still nothing. the manifold is still hot, but not excessively so - i can put my hand on it by the injectors.

    i'm about to make my family late, so i call my son to come rescue me in the truck. he arrives with my tools, i pull all the plugs - they are bone dry, not a hint of fuel - deposits are all a nice mocha. i crank the engine w/the plugs out to blow out some air, then put in the plugs and it fires right up.

    unfortunately this nonsense makes us miss our ferry and the vacation is delayed - anniversary, i'm in the doghouse. mighty pissed off.

    while this doesn't seem to be the "classic hot-start" issue, i'm not sure WHAT my z's problem is, but it DOES seem to be directly related to heat soak - seems to be happening every time i have the typical situation: hot car, 10-20 min. sit, then problem starting, then starts when it cools down.

    i've got to get this figured out, as the car is next to useless if i can't depend on it to start without a half hour of nonsense every time it's hot. do i really have to spend $1,000 on headers, fuel rail, injectors and revised exhaust just to have a car that will start regularly?!?

    ugh.

    if it weren't such a cool car, i'd have kicked it to the curb already.
    '78 280z - Daily driver/work in progress...

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    My '77 is stock except for K&N air filter and cold air intake, and I have exactly the same problem as rossiz describes. In fact, last time out, the car just quit at a stop light and I had to have it towed home. No Son with truck and tools to come to my rescue.

    So reading thru here, the possible fixes are '79 fuel injector fan, '79 fuel rail, after market header, or fuel accumulator. Guess I'll start with the first one and see if that solves the problem.

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    These last few posts are interesting (although painful to read in rossiz's case). ZXR616 has a header, as does siteunseen, the only two cases of "no problem" so far. ZXR616's case is a little bit confounded by the fans, but they probably don't run when the car is parked (do they?).

    I do things to my car that I wouldn't normally recommend to others, although the experiments are typically hidden so the car still looks good, but in this case I'll just describe my ugliness. If you get desperate to just know that the problem might have a solution, go to the wrecking yard and get 2 heat riser tubes from an 80s - 90s Chevy S10. It's a flexible fiber/foil tube that fits perfectly over the nose of the ZX fan. Get a one hour bathroom fan timer from Home Depot. GE brand. Get a ZX blower, or a marine bilge blower (Amazon). Mount the blower somewhere in the engine compartment, tape the tubes together to give the length to go from blower to injectors, punch sizable holes in them over the injectors, mount, attach and wire everything together. The purpose is clear so details aren't necessary. The tube will lay down right on top of the engine, the hardest part is squeezing it between the hood latch and the valve cove. But it's flexible. The timer is attached to the steering column. I reach down and turn it on whenever I park.

    I used a lot of zip ties for my experiment, which is still there because it works so well. I have noticed though, recently, that I get a little stumble sometimes, even with the fan on. I wouldn't be surprised if gasoline formulations are changing. But if I forget to turn the fan on, it's a guarantee that I'll have a serious heat-soak problem.
    On the stock ZX fan setup - apparently the ZX fans don't turn on much using the water temperature switch. Better to use a manual timer.
    1976 280Z, with some minor modifications

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    ZXR616, I think the fuel regulator, header and possibly megasquirt are the reason you don't get heat soak. Have you tweaked your MAT values or cranking pulsewidth in megasquirt ?


    edit: from the mazda megasquirt forums

    "i have upped my cranking pulses 30% to accomodate the e85"
    Last edited by hr369; 04-14-2014 at 02:37 PM.

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    at this point the z is officially downgraded from DD to "toy" status, as i can't count on it to actually fire up when i need it. currently sittling in a coffee shop killing however much time it will take for the thing to decide it's cool enough to start again.

    the thing that has me perplexed is that while i'm having no-start issues for sure every time it's hot, it's also been hard to start a few other times when it WASN'T hot, so i'm not convinced that heat soak is my only problem. i'll try to lay out the symptoms and maybe some sage advice can come my way.

    it has three distinct starting modes:

    mode #1 - starts right up, immediately and runs great.

    mode #1.5 - gives a quick fire at first crank, then dies immediately and needs a great deal of continued cranking until it starts, then it runs just fine.

    mode #2 - gives a quick fire at first crank, then dies immediately and WILL NOT START no matter what, for 1/2 hr. or so - not even a pop, nothing.

    #1 is the norm first thing in the morning, but i've recently had #1.5 happen a couple of times first thing on a cold motor, and last night on a fairly cold motor. it started fine, i then drove a mile up the road to pick up my daughter and came back out and it was a #1.5 while humiliated teen sighed and rolled her eyes with embarrassment.

    just now, the engine was hot, it's a sunny, mid-60's afternoon, i stopped at the hardware store for 10 min. and then the z gave a big fat #2 with NO start whatsoever. yes, the #2 moniker is a concious refernce to what it feels like to sit there wondering if i'm going to get home/to work/that meeting/etc. or not. i took out the plugs and they are all bone dry, which tells me i'm not getting any fuel. my pressure guage is between the filter and the rail and measures almost 40psi when i'm cranking or when i pull the solenoid wire off the starter and run the fuel pump w/the key to try and prime in more cool fuel.

    it seems like the injectors just refuse to open at all. could this be an electrical issue?? the odd thing is how it runs perfectly whenever it runs - just has this starting issue. is there a different control for firing the injectors during cranking vs. when it's running (like the fuel pump relay logic)??

    i am completely flummoxed...

    help.
    Last edited by rossiz; 04-15-2014 at 02:28 PM.
    '78 280z - Daily driver/work in progress...

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    As noted earlier, it doesn't really sound like the "heat-soak" problem. The fact you don't even get a pop sounds more like a spark issue. Are you still using the stock ignition module? With the ballast resistor? Next time, or right now, you might check for spark to be sure it's actually a fueling problem.
    1976 280Z, with some minor modifications

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    Could his fuel pump be overheating? Maybe clean and re tighten the terminals.
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Quote Originally Posted by rossiz View Post
    it seems like the injectors just refuse to open at all. could this be an electrical issue?? the odd thing is how it runs perfectly whenever it runs - just has this starting issue. is there a different control for firing the injectors during cranking vs. when it's running (like the fuel pump relay logic)??
    There is an enrichment circuit built into the ECU which adds extra fuel while the engine is cranking. It tails off over the next thirty seconds or so after the key is released back to ON. But other than that, I'm not aware of anything different about firing the injectors between START and ON.

    My money is on fuel, but just a quick test to make sure? Pull a vacuum hose and give a quick shot of starter fluid into the intake manifold? Should pop on that for a few seconds if there's spark.

    Another idea would be to disconnect one of the bullet connectors going to the temp sensor (either one will work) and then try to start it. This will fool your ECU into thinking your engine is Antarctica stone cold and add extra fuel accordingly. Pull it and see if it will start then. It'll billow clouds of smoke if it starts, but while it's running you can then reconnect the sensor bullet.

    Quote Originally Posted by siteunseen View Post
    Could his fuel pump be overheating? Maybe clean and re tighten the terminals.
    Doubtful. He says the fuel pressure looks good even when the problem is occurring.

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    i believe my problem is an EFI electrical issue which has somehow been exacerbated by or is simply coincidental to hot-start conditions, so i'm going to start a new thread to try and keep this thread on-topic.

    let's just say today wasn't a banner day for the z...

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    '78 280z - Daily driver/work in progress...

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    I had a thought . I put a ZX distributor on my '77. I have a black w/blue striped wire that's energized from the key at start then loses it when it clicks back to the on or run? notch. What if you wired the CSV to that wire? It would purge the fuel briefly and give it a shot of fuel on start up no matter how hot it was.
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    In all this discussion of what 'it' could be, don't forget the value of having a fresh distributor cap and rotor. They do wear out, and Datsun said to replace them every 12 MONTHS in the manual. That, combined with a fuel check valve after the filter has helped my vapor lock problems here in Texas about 90% better. And it is vapor lock ,people.

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    Please give more definition of "vapor lock". I don't understand what you mean by the term. What, in detail, is happening?
    1976 280Z, with some minor modifications

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    txv, you funny too. Not hot enough back by the pump to vaporize the fuel.
    Vapor lock - Wikipedia, the free encyclopedia


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    To be clear, the fuel obviously vaporizes in the fuel rail and injectors, where the hot is(engine block). Mmkay? Not back at the pump. Once that happens, you are done until the fuel returns to the liquid state. That is the 'what' .
    As to 'why', various reasons all boil down to the boiling point of the fuel in your fuel system, which can be controlled by pressure, temperature, and fuel blend.
    Did I really type all that?

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    Quote Originally Posted by txvepr View Post
    To be clear, the fuel obviously vaporizes in the fuel rail and injectors,
    Now you're changing your story. Or you didn't read the link you posted, person.

    From the Wiki link (bold italics mine) - "It occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system,"


    On a progressive (as in making progress) note, I'm 80% of the way to trying out some 1990 era injectors, of the four hole, high impedance type. Just to see if any design improvements happened along the way. I notice that the high impedance injector pop open with less voltage, even though resistance is higher. More windings, I think (another area I don't know well though, like transistors). If it's a mechanical binding problem, or solenoid resistance increasing due to heat, maybe more opening force will help. Hopes aren't high but I think it's worth a shot. I'm bypassing the resistor pack so there's a lot of new happening.
    1976 280Z, with some minor modifications

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    Not my story, focus on temperature and pressure. The higher your fuel pressure is, the higher its boiling point is, just like a radiator. If the system does not hold pressure when its stopped, that gas boils, making vapor, and voila. No liquid.
    I've watched gas start to boil in ambient pressure at around 140F. You can believe its at least that when the engine is stopped after 10 minutes easy.
    Good luck with the windings.

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    Here's an interesting post I found while Googling around (this is not a reply or reference at all to the last 7 posts here),

    ignition upgrade and timing bump (no 56K) - Page 106 - FSB Forums

    Post #2108 (longest thread ever), bottom image with the diagram, talks about deposits on the single pintle design. Could help explain a pintle binding theory. Regardless, it's interesting reading, to me anyway.

    I've been driving around with new injectors for the last 5 days, but am waiting for the next couple of days here in the Portland metro area to give them a true test, it's supposed to hit 80. But I've also changed to a straight-shot fuel rail so results won't be assignable to a single cause. But all of the changes combined seem to be working.
    1976 280Z, with some minor modifications

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    Z geek at large FastWoman's Avatar
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    Zed, I suppose deposits binding the pintles could explain some hot restart issues, but certainly not all. I'd offer the following thoughts:

    1. I continued to have some hot restart issues even after replacing my injectors with new ones. Although the hot restart was improved, I did many things as a part of my intake overhaul, and it's difficult to say specifically what improved my situation.

    2. The deposits on the pintles are going to be varnish. Varnish is hardest when cool, so I would think the deposits would cause the greatest problems with sticking when cool. But contrary to this notion, time and cooling reliably resolve this restart issue.

    3. One could argue that it's a thermal expansion issue, but that would depend entirely on the materials involved. If all the parts are made of the same material, thermal expansion would have no effect on their relative fit. So a steel pintle in a steel sleeve would not tighten with either heating or cooling. Of course I can only speculate as to the materials typically used in an injector. However, I would think that any thermal expansion jamming that would occur in a heat-soaked engine could also occur in a running engine, particularly when idling on a hot road in the middle of summer. But we don't hear about that.
    Last edited by FastWoman; 04-29-2014 at 11:41 AM.
    My last three sports cars while I still owned all three:

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    1978 Datsun 280Z (enjoying very much )

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    I thought that I would post the link mainly as food for thought. Single pintle versus four hole. I don't even know that the description in the drawing is right, since it talks about a plate but the diagram shows a tapered seat valve.

    I'm going to start another thread with the details of what I did. My experience with cooling the injector bodies makes me think the problem is in the injectors but I don't have the definitive experiment done, with other variables controlled.
    1976 280Z, with some minor modifications

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    Here's the link to my other thread. Still collecting information.

    http://www.classiczcars.com/forums/f...tml#post455660
    1976 280Z, with some minor modifications

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    Lance Corporal of Marines TheCrazySwede's Avatar
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    A few months ago when I was experiencing the hot restart problem, my local Nissan/Datsun mechanic suspected that it had to do with the fuel mixture used during winter time. I wasn't sure if that was true or not, because I can't remember if I experienced it last year. Now that it's summer (I live in CA, so it gets pretty warm) I've been driving my car, just the same way it was during the winter, in much warmer circumstances, and yet I'm not experiencing the hot restart issue anymore. I've tried to replicate it (Drove it hard, parked it in the sun...waited 10-15, and started it) but it just starts right up without a single moment of hesitation.

    Anyone else experience this? Perhaps in my case, the guy I spoke to was right.

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    i've been quiet on this thread for a while, since last time i chimed in there were electrical issues clouding the problem, and i wanted to be sure i had good, consistent info to report.

    it's been warm here in seattle, and i've been plagued by constant hot start problems. the car runs fantastic, plugs seem decent color, i just ran seafoam through the intake the other day and my idle has gotten much more stable, the only issue is starting when it's hot. the car starts like a champ in the morning - almost instant. now that it's hot outside, when i stop for 5-10 min. the car has a very predictable pattern: it fires up for just a second, dies, then will not start at all. doesn't matter if i leave the hood up, it just seems that the initial heat soak is flashing the fuel pretty quickly for me.

    strangely, for me priming the fuel actually works consistently to get it going. i hop out, pull the wire from the starter, hold the key for 30-45 sec (a long time, yes, but it does work) and then she'll fire up - if not, i'll get the same sort of 'almost start' and have to repeat the process, but once it starts it revs right up and it's business as usual.

    the other odd thing is that if it heat soaks, the vapor will stay behind the injectors for a very long time. i took my daughter to her ballet recital at 4:00 and it was hot out - shut the car off in a parking garage (at the perimeter, sun on the hood) and came back at 6:00 and it did the 'almost start' dance, needed 30 sec. of priming and then fired right up.

    i'm going to put a toggle switch in the cabin to cut the starter wire so i don't have to jump in and out of the car every time. hope that will work until i can save up for a header. i'm convinced the header will work to reduce the heat soak. i'm also planning to look into the multi-spray injectors and a different rail.
    '78 280z - Daily driver/work in progress...

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    Sorry you're still having hot restart issues, Rossiz! As an alternative to a starter kill switch, you might wire a switch to deliver +12V to the coil of the fuel pump relay. It would be a priming switch, so to speak. (That's what I did on my car.)

    I'm anxious to hear what does the trick for you, since you'll be trying a few approaches.
    My last three sports cars while I still owned all three:

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    I wonder if there's something odd going on with your fuel pump control relays, that gets corrected when you disconnect the starter solenoid. Maybe the voltage drop from turning the engine is screwing up the fuel control system. It might be worthwhile to connect a fuel pressure gauge, then pop it out to where you can see it while you have the no-start condition. The symptoms seem more like no fuel pressure at all. The priming step might just be building up pressure, which allows the engine to start, then fuel pump control returns when you're off the starter.

    You're not conforming.
    1976 280Z, with some minor modifications

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    i have a fuel pressure gauge between the fuel filter and the rail - the pump check valve is holding pressure, the gauge is at a solid 35psi when i go to start. when i pull the solenoid wire off the starter and turn the key, i can watch the needle bump up a psi or two as the fuel circulates, and i can hear it running through the fpr. then when i re-connect the starter, it fires up.

    i'm sorry, but i've never been very good at conforming...
    '78 280z - Daily driver/work in progress...

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    Another Data Point:

    1976 280Z, MSA Coated 6-1 Header, new Standard Motor Products FJ707T injectors. I was just out running errands, 84 degree day, one 30 minute stop and one 10 minute stop. Never a hint of this problem, not today and not prior to today since I got it on the road in April (and have been driving it most days). It always fires right up, hot, cold, warm, or luke warm.

    Probably not of consequence but I have a rebuilt ZX distributor/ignition module (with appropriate wiring mods) and a rebuilt air flow meter. I believe the fuel pump was recently replaced by the PO.

    Dan
    Last edited by sscanf; 06-02-2014 at 12:51 PM.

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    You have the same setup as siteunseen. Header and FJ707T injectors. That's two wins for that combination, but still leaves the question of header or injector.

    Here's something generally interesting on injectors. BWD and Standard are made by the same organization, and the high end BWD's have the FJ type of output (see links below). When I bought my first set of new injectors, I went for the cheaper ones,with the single pin pintle design, like Nissan stock. A few more dollars and I might never have had the problem, assuming injectors alone are the solution. The price difference seemed higher back then.

    List: Fuel Injector - 1978 Nissan 280Z | O'Reilly Auto Parts

    BWD 57519P - Fuel Injector | O'Reilly Auto Parts


    Edit - I shouldn't leave out FastWoman's Standard FJ3 injectors either, with stock manifold and heat shields (but a wrapped/insulated fuel rail). Reported to have occasional hot start issues, but not significant, if I recall correctly. That's three FJ injector winners, no FJ losers yet.
    Last edited by Zed Head; 06-02-2014 at 03:46 PM.
    1976 280Z, with some minor modifications

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    it looks like the 57519P has a different plug/connection - is there a removable insert in there so the oem style plugs will work? i just bought and wired in a complete set of new plugs to fit the oem injectors (and csv)

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    Hey Zed, I also have the FJ3's and exhaust header installed with no hot restarts.

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    And let me add that what I thought was a "hot restart" earlier this year was not. It is the oxygenated fuel we have to use during winter months. Makes the car seem like its running lean, leaner than it should.

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    Quote Originally Posted by rcb280z View Post
    And let me add that what I thought was a "hot restart" earlier this year was not. It is the oxygenated fuel we have to use during winter months. Makes the car seem like its running lean, leaner than it should.
    Same here!

  87. #87
    BackDoorZ BackDoorz's Avatar
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    Vapor Lock, Heat Soak, VooDoo, whatever you wanna call it ...
    ________________________________________
    I have read a lot about "heat soak" and "vapor lock" for quite a while now. I was always under the impression that those two "quirks" were not likely to happen on FI type engines. If you do a "Google" on the subject, you will find a vast number of folks that say it can't happen. After saying all that I will add my spin.

    I have a 1976 280Z, automatic, A/C, with ~155,000 miles. I am the original owner. The car is all original under the hood. This car was my daily ride for about 10 years (1976-1986). I live in N.C. where it gets 90 to 100 degrees for most of the summer. From the first day I started driving this car, till I parked it, I never experienced any type of "heat soak" or "vapor lock". I could go anywhere, park, come back out in 15-20 minutes, and she would start right up with no problems.

    For about 6 years (1986-1992) this car was parked in my garage. I did not drive it. I decided to start driving it again. I did some work getting her "road ready". I started to drive this car on a limited basis, still experiencing no "heat soak" or "vapor lock".

    After about 4-5 years I noticed that on rare occasions the car would seem to, what I thought, flood for just a brief time after about 15-20 minutes with the engine off. As the years have gone by, I can tell that this problem has gotten progressively worse. Now it is like this everytime it is parked for 15-20 minutes.

    I have changed several items in hope of correcting this problem. New fuel pump, new FPR, fuel injectors cleaned and tested, cleaned all electrical contacts, new AFM, cooler thermostat, new fuel filters (G3 & under hood), complete tuneup (including adj. valves), checked for air leaks, etc., etc., etc. I installed a switch underneath my dash to allow me to just run the fuel pump before I tried to start the engine, hoping to pump cooler gas around the fuel rail. I have seen very little improvement if any.

    My conclusion about this problem ... gasoline. The gasoline that I was putting in this car in the 70's and 80's in nothing like the gasoline that I'm using today. Each area of the country seems to have their own blend for summer and winter.

    I intend to try and burn ethanol free gasoline for awhile and see how that works. I also plan to take the fuel rail off and wrap it and the fuel injectors in some type of heat wrap. My thinking here is maybe insulating the fuel system from the heat as much as I can.

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    Welcome to the club and thanks for adding. Fuel quality has been discussed here and there. Unfortunately, most of us have to live with whatever is in the local station's tanks.

    So far, people with Standard FJ707T injectors, aluminum fuel rails and headers, Standard FJ3 injectors with headers (Post #84), and me with Bosch 0280 150 901 injectors, aluminum fuel rail, and stock manifolds, seem to have eliminated our hot start problems. Although it's not clear if rcb's issue will come back in the winter-time.


    Here's a really interesting presentation from Lawrence Livermore National Laboratory showing how ethanol affects vapor pressure, but also showing that gasoline can be different in different areas of the country. That's one more thing that gets the discussions messed up, one guy says I have these parts and no problem, another says I have the same parts and have the issue every day. But they're talking about different petroleum distillations, and different ethanol percentages. It's worse now than in the past because modern cars are designed to adjust for the variation.

    http://www-erd.llnl.gov/ethanol/proceed/autoupd.pdf
    1976 280Z, with some minor modifications

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    Registered User S30Driver's Avatar
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    I will be very interested to hear the outcome of BackDoorZ's ethanol free gas test.

    My car has the stock green injectors, a Pallnet aluminum fuel rail, stock manifold & soon to install my chromex coated main heat shield.
    1977 280z 06/77

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    '77 280Z, stock injectors (recently cleaned and flow-matched, two were replaced) on stock fuel rail. MSA 6-1 header with stock heat shield. I drove it daily until I was out of the area for pretty much all of 2013 without a problem. Came back in November and went right back to it with no issue whatsoever. It sat parked since March and I just drove my truck but now that the weather is nice (and hot...) I decided to bring out the Z. Ran it for a while and took it around the block to make sure it was ready for the commute. Ate dinner and went out to start it back up and nothing. Hot weather? Maybe. I didn't try the usual starter disconnect/run the pump trick because I was... disappointed. That worked for me in the past (I feel your pain, rossiz, and I was also thinking about a toggle switch for this purpose). I will tinker with injector fans and see if that helps.

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    And the million dollar question: Did your car start up effortlessly after it cooled off? Don't get too heavy into the diagnostics yet. The classic hot-restart issue is that the car starts fine cold, you run it around, getting the engine and engine compartment good and toasty, you shut down, you return 10-15 later, and the engine won't fire up. Let it sit for another hour, and it will start up just fine. Your case is interesting because you have headers.

    I assume you have fresh gas in the tank?

    I, too, am interested to hear Backdoor report back. I tried running some ethanol-free gas here, and I didn't have a hot restart problem, but my hot restart issues are too seldom for me to conclude whether that was just by dumb luck. The fuel did make my engine run a bit too rich, though, which is why I went back to the ethanol blend. Remember, I have the potentiometer mod to richen the mixture. I could re-tune for the ethanol free gas, but I don't want to have to buy all of my fuel from one gas station.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    so i'm not sure i can offer anything conclusive here, as i've done quite a few things at once and can't tell for sure which one did the trick, but it's been hot as all get out here in seattle the past few weeks (hot for us at least, upper 80's) and the car has been starting just fine. when it's really hot it runs a little grumpy for a few seconds, but cleans right up with a rev or two on the pedal. i'm using the cheapest gas i find (as always) which typically has ethanol in it.

    mods:

    new n42 head
    shaved/cleaned manifold
    new ceramic coated 6-1 header
    home made "ghetto-style" single run fuel rail (cut from oem)
    all new injectors (nos oem)
    Last edited by rossiz; 08-08-2014 at 06:51 PM. Reason: mis-labeled the head...
    '78 280z - Daily driver/work in progress...

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    I am inclined to blame the fuel rail after reading what rossiz said. I had never seen the fuel rail mod until I just Googled it... interesting. The gas in it it kinda old (April). I am about to run some errands in the Z and put some fresh gas in the tank. Wish me luck and I will report back.

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    quick edit: the new head is an n42...
    '78 280z - Daily driver/work in progress...

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    Yesterday I drove around all day. Ran errands with lots of 15 minute stops, drove in traffic, and opened it up on some of my favorite lines. Ran like a champ and started right up every time.

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    Update: I was out of town for five days and came back. Z is still running and starting perfectly. This is still the same not-so-fresh gas that I had when the hot start issue popped up the one time.

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    So the summary might be that you had one instance of the car not starting at all, and whatever the problem was went away? But since then it's been starting fine. You are essentially all stock, including injectors, except for headers.

    So, headers might be a simple one component solution to the problem. Possibly due to reduced heat-holding mass by the injector bodies.

    Thanks for reporting back. Things will get clear, piece-by-piece. At least there will be a few potential solution paths to try for anyone that can't stand it anymore.

    For the record, my 14mm, o-ring, 1990, high impedance 4 hole valve injectors on a straight-shot aluminum fuel rail haven't had a problem and it's been up in the 90's and high 80's on a regular basis here. Odds are it's just the aluminum rail and its extra fuel volume dissipating heat, as the fuel vaporizes from the injectors and recools in the rail (Fastwoman's heat-pipe theory).
    1976 280Z, with some minor modifications

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    Up until recently, I occasionally suffered from the classic hot start issue.
    Since I had both manifolds off to replace the gasket, had my main heatshield plated with chromex, coated the stock exhaust manifold, I have had no problems. And it has been consistently hot here for the last 6 weeks.

    Stock injectors with Pallnet aluminum rail, stock exhaust, chromex heatshield.
    FWIW
    1977 280z 06/77

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    Thanks for the addition to the thread. The math seems to be leading to the conclusion that the typical Pallnet style aluminum rail (AN -6 size bore), with stock heat shielding, could solve the hot start problem alone. Heat dissipation is the key.

    Just summarizing, for anyone looking for the simplest, and probably cheapest overall solution. You can get the rails with barbs, and could even get an extra port for the CSV, keeping all of the stock functions and most of the parts. Headers and/or new injectors are probably not necessary to get rid of the problem.
    1976 280Z, with some minor modifications

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