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Thread: Hot Start Woes: Maybe NOT Fuel Pressure?

  1. #11
    Not really banned Michael's Avatar
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    Quote Originally Posted by Michael View Post
    Had the car been recently worked on before this hot start issue(for anything)? There is a reason I'm asking.
    I'll ask again.

  2. #12
    Junior Member ASquared150's Avatar
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    Quote Originally Posted by Michael View Post
    I'll ask again.
    Haha sorry Michael - your original comment got lost in the fray. I just bought the car in September of last year. Brought it out to Mike at DMC MW in October and they did a make-run and first-timer's inspection. Post-inspection there was a lot of work to be done in the fuel system, namely a new pump and cleaning out the gas tank. Also replaced the fuse box and and a ball joint and got all new brakes. Also had the Eibach springs installed (which certainly wasn't necessary at the time but I couldn't stand the front wheel-well gap). And a few other things like new door/hood struts etc.

    But the only work done on the car since October has been me doing the accumulator, check valve, and o-ring.

    Quote Originally Posted by Bitsyncmaster View Post
    Your result will tell you if it is a rest pressure problem or to look elsewhere for the problem.
    Quote Originally Posted by DMC5180 View Post
    The next time you go to do a Hot start and it doesn’t, unplug the blue CSV connector and try again. IF it starts, this is an indicator that the TTS has been bypassed to ground and the engine is getting too much fuel when hot.
    Quote Originally Posted by Rich View Post
    About initial diagnosis question: If you or DMCMW can verify that the system holds at least 25psi for 10 minutes after engine shutoff then you'll know if you need to keep troubleshooting for fuel leakage or work on non-pressure causes. The air meter plate test is a good starting point but you can't get a number from that.

    About your CSV question: Agreeing with Dennis on the TTS check and adding this. Among the potential leak points, most of which are mentioned in the thread already, is the CSV. If it leaks enough - or if any of the injectors leak - then the system won't hold rest pressure. So, is it possibly a leaky CSV? Yes, but not likely. You could pull it and look for fuel leaking with ignition ON, engine off, TTS & CSV plugged in as usual.

    Be safe around pressurized fuel components.
    I'll take a few taps on the air meter plate and check out the CSV connector next time I'm with the car (I keep it parked in my dad's garage about 30 minutes from my apartment). Possibly later today.

    Thanks everybody for the advice/assistance/etc!
    Last edited by ASquared150; 03-11-2018 at 05:49 PM.

  3. #13
    Member
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    My VIN:    10769 1246

    possible solution

    Hello,

    I've been having the same problem with 1246 since I bought it in December. I've driven it about 800 miles. It started fine when cold but it wasn't holding rest pressure and I had to crank and crank to start it again if it sat for more than a few minutes after shutting it down when hot. I replaced the o-rings and fuel check valve, and checked the POA to no avail. The accumulator is less than 3 years old.

    Yesterday I decided to look at the vacuum reservoir in the driver's side pontoon. There is a rubber cap over one of the fittings and it was completely rotted. I replaced it with a new one (3/8") and today for the first time I've had no problem. I was stopped for a while doing errands at two different places. The car started as soon as I turned the key even though it was not completely cooled off. I checked and it is now holding rest pressure.

    I hope this helps.
    Rich
    Last edited by Rich06; 03-11-2018 at 08:04 PM.

  4. #14
    One of those purists you keep hearing about. sdg3205's Avatar
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    Hi rich. That vacuum bung has nothing to do with rest pressure. Just a stroke of luck. Your issue is probably unresolved.
    Dave

    Here, somewhere.


  5. #15
    Member
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    Quote Originally Posted by sdg3205 View Post
    Hi rich. That vacuum bung has nothing to do with rest pressure. Just a stroke of luck. Your issue is probably unresolved.
    Thanks Dave,

    I kind of thought that but wasn't sure. It just seems strange that the car had no hot start issue for the first time today and is holding rest pressure. The outside temp was not any different than what we've had. I've had the problem for almost 3 months. I have done some other things such as replacing the fuel lines, etc., but didn't do anything else yesterday.

  6. #16
    Senior Member Rich's Avatar
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    Quote Originally Posted by Rich06 View Post
    ....today for the first time I've had no problem. I was stopped for a while doing errands at two different places. The car started as soon as I turned the key even though it was not completely cooled off. I checked and it is now holding rest pressure.
    Rich
    That sounds good but maybe the problem is still there under other conditions? Depending on the time you take between shutdown and hot restart you may get varying results. If you wait less time after shutdown the rest pressure may still be above minimum, the fuel won't vaporize in the high-side lines and it will hot-restart. But in other circumstances with longer dwell time the fuel pressure may drop further and you get stuck.

    You mentioned it is now holding rest pressure. Did you measure it? If so was it above 25psi 10min after hot shutdown?

    Hoping it is indeed back to normal somehow...
    March '81, 5-speed, black interior

  7. #17
    Junior Member ASquared150's Avatar
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    Thanks for the tip Rich06 - here's hoping your issue really is fixed. Also sorry to kinda take the thread back... but I did make it out to my dad's today and ran all the tests/checks I could in the short time I had:

    First thing I did was pull the cold start injector to make sure it wasn't leaking. It was a bit dirty but I cleaned it up and turned on the ignition, no leak. Had my dad crank the motor briefly and it sprayed a nice little mist of fuel just like it should.

    So I re-installed it and took the car out for ~20 minutes to get it warmed up. Came home, started a timer and pulled the air box. Tapped the air plate a few times every minute and after 20 minutes it still had back pressure so I put the air box back on and went to start the car. Which is where this gets a little sticky.

    Normally 20-25 minutes is the perfect amount of time for vapor lock to set in, but the car started right up. Idled a little rough but steady, and got smoother if I gave it a little gas. Shut it down and unplugged the CSV. Started right up again. I figured the 20 minutes spent tapping the air plate must've been enough for it to cool down (even though it usually takes more like 35-45 minutes to get over its vapor lock.)

    Waited another 5-10 minutes and tried starting it again with the CSV still unplugged. This time it didn't start, but that's probably because it was cold at that point. Plugged the CSV back in and it started - though it idled rough. Unplugged the CSV again for the hell of it and started right up again, but this time idled smoother.

    ...So, I have no idea what's wrong at this point. Any thoughts?

  8. #18
    Senior Member DMC5180's Avatar
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    Well, youíve had positive results, but youíll need to run the test again. But, let the engine get hot so the Fans cycle at least once.

    Then do your typical delayed hot start routine. Donít unplug the CSV this time. If it doesnít start right away, then and only then, try it with the CSV unplugged.


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  9. #19
    Junior Member ASquared150's Avatar
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    Quote Originally Posted by DMC5180 View Post
    Well, youíve had positive results, but youíll need to run the test again. But, let the engine get hot so the Fans cycle at least once.

    Then do your typical delayed hot start routine. Donít unplug the CSV this time. If it doesnít start right away, then and only then, try it with the CSV unplugged.
    So - went back out in the car for a 30-minute drive. Fans cycled multiple times. Came home, let the car sit for 20 minutes and went out to try and start it up again (for the first time hoping for vapor lock.)

    On my first attempt (CSV still connected) the car cranked and turned over but immediately died. That actually happens somewhat frequently with my hot start issue. Tried it again immediately afterwards and nada. Just starter motor, no turnover.

    Then I pulled the CSV, turned the key, and still nada.

    So I think we can rule out the CSV malfunctioning. Yay?

  10. #20
    Senior Member Rich's Avatar
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    Quote Originally Posted by ASquared150 View Post
    So - went back out in the car for a 30-minute drive. Fans cycled multiple times. Came home, let the car sit for 20 minutes and went out to try and start it up again (for the first time hoping for vapor lock.)

    On my first attempt (CSV still connected) the car cranked and turned over but immediately died. That actually happens somewhat frequently with my hot start issue. Tried it again immediately afterwards and nada. Just starter motor, no turnover.

    Then I pulled the CSV, turned the key, and still nada.

    So I think we can rule out the CSV malfunctioning. Yay?
    Sounds like the CSV is fine. It isn't leaking per your observation.

    The better news, if you can call it that, is that you can more or less replicate the hot-start issue. Is that correct?

    If only you can get a fuel pressure reading to go with the repeatable hot-start issue....if you can know from data taken before/during hot-start-fail events that fuel rest pressure is below spec then you'll know focus on finding the leakage.
    March '81, 5-speed, black interior

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