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Thread: Cold Start Valve

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    Default Cold Start Valve

    About a month after I bought my car every time I would start my car it would crank and crank and crank and crank till finally it turned over. This got worse and worse over time but now it is just the same every time I try to start my car. I have been told it could be a cold start valve but other people say it has to be really cold outside for the cold start valve to even turn on. Please help, I need to get her running right again. It is a 1983 280zx non-turbo

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    I would do a fuel pressure test. Sounds like the pressure is leaking back to the tank or a leaky injector. What is your year model, you can activate the fuel pump to see if it will "prime" the system and then start the car.

    I have a 77 model and the pump is activated by the AFM. With the key in ON I can run the pump by pushing the AFM open. Fitting a guage after the fuel filter will also tell you a lot about the condition of the pump and FPR. You will need one that can handle up to 50psi. At idle it will be around 30psi, but can go to 36psi with not manifold vacuum.
    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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    Mine is a 1983 S130, I was just wondering how do you check the fuel pressure from the fuel filter

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    Do you have a gauge yet? Do you have any plumbing experience?

    If you are not handy with threaded fittings and making them leak-proof you should probably buy or borrow a fuel pressure measuring kit. It will come with a plastic T-shaped fitting and a short piece of hose that are inserted between the filter and the fuel rail. The old fuel hose will be difficult to remove and may need to be cut off. Gas will spill. If you need to cut the old hose off you can just cut it and insert the gauge then replace the hose with new when you're done. Quicker.

    If you know how to work with fitting you can buy a gauge and fittings and fabricate your own gauge system. Depending on the price of brass fittings at your location it might be cheaper to just buy a gauge kit at a parts store. The hose is 5/16" internal diameter.
    1976 280Z, with some minor modifications

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    Here's what I did at first. You can reach across the valve cover and rotate the throttle rod.

    here's a good detail of parts needed to put together a gauge, http://www.classiczcars.com/forums/f...dent-help.html, read post #31. You'll be able to get the "T" and the hose barbs from an auto parts store, seems like I found the T in the brake line fittings cabinet.
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    Last edited by siteunseen; 11-20-2013 at 10:28 AM.
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    I had a similar problem you are having. My 280Z was hard to start when it stood longer than a day or so.
    If you follow the instructions from Zed head and siteunseen you can test the different sections of the system to find where its leaking.
    I found my leak (check valve in pump) by doing these steps.
    1: Fit pressure gauge between filter and fuel rail.
    2: Run fuel pump until pressure reaches peak. 36psi. (engine not running).
    3: Check leak down rate. (psi/minute)
    4: Clamp the fuel hose shut. After the pressure guage. (I fitted new hoses and used a G clamp. You can change the hoses when fitting the pressure guage. Old hoses don't like being clamped shut very much).
    5: Run the pump for short period to build up pressure. Be carefull not to overpressurise the system. You don't have the FPR to limit maximum pressure.
    6: Repeat step 3. If the leak rate remains. The leak is in the pump. If it doesn't loose pressure the leak its further down the system.
    7: Remove clamp. Run pump to build up pressure and then clamp to Fuel return line (From FPR back to tank) shut.
    8: If it holds pressure, its your FPR. If it still looses pressure, it must be leaking through one or more injectors or the cold start valve.
    I lifted all the injector with them still connected to the rail. Took some time getting them out, but then you can see if they leak with the pressure test. The cold start valve is easier to remove ( keep hose connected) and test.
    Goodluck hunting.
    Chas

    Edit: If you don't want to clamp the hoses, you can remove hose from downstream pipe and plug it with a 5/16" bolt ( with unthreaded section.) or a piece of round bar will work.
    Be carefull removing the hose. Fuel WILL spray everywhere even with almost no pressure.
    Last edited by EuroDat; 11-20-2013 at 02:40 PM.
    Chas
    5/77 280Z HLS30 403100 with some modifications
    Original colour: 305 Light Blue. The PO changed it to Red

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    Can I leave the gauge on there once I'm finished

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    Yes you can, most people mount them closer to the fuel rail on the drivers side. I took mine off when we figured out the problem. Now it's with my other test tools, I'm sure I'll need again.
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    I know it has been a while but finally I found time to do a fuel pressure test. I hooked up the gauge from the fuel filter to the fuel rail. I had good pressure and it didn't drop very fast. Is that the only place I have to check the pressure or are there other places that I didn't understand from what you guys said? If I don't have to check the pressure anywhere else what else do you guys think is the problem with my car. Any suggestions help- Thanks

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    When I bought my 240 it was my 1st carbureted Z and I was thinking the reason I was cranking and cranking with the choke lever pulled was the carbs needed to be filled with fuel. Turns out my valves were out of adjustment. After getting them back to specs it cranks on the 1st turn over with full choke. They weren't unusually loud though so it was just luck that I even checked them, actually it was a rainy day and bored to death project. I'm no certified mechanic but I think they DO need the CSV just like my 240 needs to be choked. I left mine unplugged accidentally and knew right away something was wrong but your '83 may be different than a '77. Take it out of the manifold and put it in a glass jar to see if it's squirting fuel, 2 phillips head screws I think. Maybe the connector is bad or needs cleaning? Good luck!

    Oh yeah, UNPLUG THE COIL WIRE before test cranking.
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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