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Thread: '77 runs for about 5 min. then dies. Cools down and runs again for another 5 min.

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    Default '77 runs for about 5 min. then dies. Cools down and runs again for another 5 min.

    Title says it all. Been searching threads and I've seen vapor lock, heat seat issues, etc but none of the symptoms seem to match my issue.

    After flushing the fuel pipes, replacing fuel filter, testing fuel pump, cleaning tank, cleaning fuel rail, replacing injectors, new plugs, new plug wires, and replacing all old fuel hoses with nice new EFI hoses the 280z roared to life. Drove it around the block a few times and everything was working great. Decided to take it for a short trip (15 miles) and had to limp home before I even got out of town. Car ran really good then started sputtering under load. Idled OK but sounded a bit rough. After several attempts to nurse it home, I finally shut it down and called a friend to come give me a tow. While waiting, I checked to make sure pump was coming on (yep), relay was clicking (yep), and nothing had come loose. When my friend arrived, I tried to get it to go one more time and it roared to life again. Drove it home and once more started sputtering when I finally got home. Waited 10 minutes and it roars to life again.

    FSM and forum searched gives me the impression it is vapor lock. Number one recommended solution has been to replace fuel rail ... trying to keep this as original as possible. Some threads I have difficulty following. Is there a "sticky" on this problem that I'm missing? Any clear posts or direction on troubleshooting? Not looking to be spoon fed but I'm am getting frustrated with posts that look promising but don't really address my problem.

    Thanks for reading my little rant ...
    '77 280z Coupe (manual) - running and almost roadworthy
    '76 280z Coupe (automatic) - rusty, rotted and almost stripped of anything useful.

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    Registered User siteunseen's Avatar
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    May very well be electrical, they fail when hot then cool down and come back to life. I think the easiest thing to do is clean all the grounds and connections you can. Takes about an hour and doesn't cost anything. Here's some help with it, http://atlanticz.ca/zclub/techtips/e...ons/index.html
    1972 240Z #918 New Sight Orange
    1977 280Z #305 Light Blue Metallic
    1972 240Z #110 Persimmons Red

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    Registered User EuroDat's Avatar
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    Next time it does it get someone to help you check for spark at one of the sparkplugs. It could be your TIU failing when it warms up. Mine was doing something similar.
    The TIU is behind the kick panel on the passengers side. When it happens again, you could try spraying it with contact cleaner to coolit down.
    I ended up replacing the TIU with a HEI module. You never know, it could be that simple.

    http://www.classiczcars.com/forums/e...1977-280z.html

    Chas
    Last edited by EuroDat; 10-22-2014 at 09:48 AM. Reason: link to other thread
    Chas
    5/77 280Z HLS30 403100 with some modifications
    Original colour: 305 Light Blue. The PO changed it to Red

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    No more body roll! SteveJ's Avatar
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    This has been covered many times. Do you have a stock ignition, or does your car have a ZX distributor?
    1. Get a can of dusting air.
    2. Drive the car until it stalls.
    3. Hold the can upside down and spray the coil. The liquid will cool the coil quickly.
    4. See if the car starts immediately.
    5. If not, do the same to the ECU.
    6. If not the ECU, do the same to the TIU or ignition module (whichever your car has).

    If that doesn't help with the diagnosis, let us know. There are some other diagnostics you can do.
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    Rust Free'ish zKars's Avatar
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    Quote Originally Posted by SteveJ View Post
    This has been covered many times. Do you have a stock ignition, or does your car have a ZX distributor?
    1. Get a can of dusting air.
    2. Drive the car until it stalls.
    3. Hold the can upside down and spray the coil. The liquid will cool the coil quickly.
    4. See if the car starts immediately.
    5. If not, do the same to the ECU.
    6. If not the ECU, do the same to the TIU or ignition module (whichever your car has).

    If that doesn't help with the diagnosis, let us know. There are some other diagnostics you can do.

    While these are excellent and well tested methods to diagnose very common ignition problem areas, I would preceed these checks by a simple check (immediately after failure) to see if you have spark or not. Just pull the high tension lead from the center of the distributor and hold the metal contact in the boot about 1/8-1/4" away from a clean bolt head (shock tower nut is my favorite). Crank the engine and see if you get a nice regular blue-ish spark. If its absent, weak or erratic, proceed with the above checks. If you do have spark, then checking ignition components falls down the list of "what to look for" quite a bit...

    I agree that in all likely hood the issue is spark related given that the fuel pump is running. Mind you only a fuel pressure check can really tell that story with any reliability. Gunked plugged up fuel systems have been all over the forum lately too.... Good luck in your troubleshooting.
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    Quote Originally Posted by ntownsen View Post
    Waited 10 minutes and it roars to life again.

    FSM and forum searched gives me the impression it is vapor lock. .
    "Vapor lock", maybe better described as the "hot start" problem, happens when things get really hot. Five minutes is barely warm.

    The "waited 10 minutes" part means something. Is it really 10 minutes or does one just seem like ten? One could be a fuel feed problem, ten is more likely something cooling down.

    Someone posted on this recently, maybe you're just reposting (?). But one possibility on the dual pickup cars, is a bad advance control circuit in the ignition module. You could test by shorting the water temperature pins so the the engine always seemed cold to the ignition module, and always used the advanced pickup. I think that I posted a different solution last time, I'm not 100% clear on what happens inside the module. Shorting the switch should work though if that's the problem, locking in the advanced pickup control.

    Edit - remembered the reason for the PO's solution on my car. On mine, one of the pickups was bad. So the PO wired them together so the module always used the same pickup, no matter what circuit the module was using. So, it could be the "late" pickup or the circuit in the module.

    If you only have one pickup, this is irrelevant.
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    Last edited by Zed Head; 10-22-2014 at 11:25 AM.
    1976 280Z, with some minor modifications

  7. #7
    1978 280Z (stock) TomoHawk's Avatar
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    Please don't use the sandpaper in the way it says on the atlanticZ website. You make make a shiny metal surface that conducts well, but it will corrode that much sooner. Use the sandpaper and knife only to get the bulk of corrosion off the part, then use DEOXIT, and the dielectric grease appropriately and sparingly.
    Drive Responsibly.
    enjoy classic Rock music.

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    Thanks for all the tips. I will start working my way through the list this weekend.
    '77 280z Coupe (manual) - running and almost roadworthy
    '76 280z Coupe (automatic) - rusty, rotted and almost stripped of anything useful.

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