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Thread: Need some help

  1. #1
    Senior Member Silverbullet's Avatar
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    Need some help

    My car has always run great, starts right up every time. The last 2 days, it starts cold, runs great, but if I park it to go buy something, and come back it just cranks, no sound of spark. I swapped the wires in back, and it starts, then swap them back, and it runs like normal...So, what is the fix?

    Craig

  2. #2
    Motors about after dark Michael's Avatar
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    I am assuming you mean the CSV/CPR plug swap?

    If so then you have a fuel issue not a spark issue and to be more precise a hot start problem. If it happened quickly, then it's probably easy to diagnose especially if you have been in the engine lately...have you been in the engine lately?

    If no, check for lose or broke vacuum lines around the back of the left valve cover where the CPR is. Also check the o rings in the primary pressure regulator. I replace mine about every 2-3 years since it's cheap and easy and hard to tell if they are bad just by looking at them.

    Truth us a dozen things can cause a hot start issue, but some quick "dead reckoning/common sense" may zero you in on the culprit quickly with minimal effort.

    The "plug swap" forces the CSV to fire no matter what the coolant temp is, so you might start at anything that could cause the fuel mixture to go south. What fuel pump setup are you running?
    Last edited by Michael; 11-13-2021 at 06:17 PM.
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  3. #3
    Senior Member Silverbullet's Avatar
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    I have not done anything to the car for like a year, just turn the key and go... I have the new all in one fuel pump, one of the 1st ones like 9 years ago, with new accumulator.

  4. #4
    Motors about after dark Michael's Avatar
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    Quote Originally Posted by Silverbullet View Post
    I have not done anything to the car for like a year, just turn the key and go... I have the new all in one fuel pump, one of the 1st ones like 9 years ago, with new accumulator.
    I was asking because I thought it might be a failed check valve but if it's a 9 year old pump itself...I wouldn't totally discount that. Probably try to repeat the issue in the shop and check fuel pressures as well as voltage to the pump (rpm relay perhaps?) I'm just throwing out guesses.
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  5. #5
    Senior Member Silverbullet's Avatar
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    Quote Originally Posted by Michael View Post
    I am assuming you mean the CSV/CPR plug swap?

    If so then you have a fuel issue not a spark issue and to be more precise a hot start problem. If it happened quickly, then it's probably easy to diagnose especially if you have been in the engine lately...have you been in the engine lately?

    If no, check for lose or broke vacuum lines around the back of the left valve cover where the CPR is. Also check the o rings in the primary pressure regulator. I replace mine about every 2-3 years since it's cheap and easy and hard to tell if they are bad just by looking at them.

    Truth us a dozen things can cause a hot start issue, but some quick "dead reckoning/common sense" may zero you in on the culprit quickly with minimal effort.

    The "plug swap" forces the CSV to fire no matter what the coolant temp is, so you might start at anything that could cause the fuel mixture to go south. What fuel pump setup are you running?
    Well, I think you nailed it... I looked and a very small vacuum line pulled had
    pulled off, looks like the hose was kind of short, and I didn't have a new hose that small so I put it back on and zip tied it for now, but I will get a longer hose pretty quick.

    Thanks,
    Craig

  6. #6
    Senior Member Silverbullet's Avatar
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    Quote Originally Posted by Michael View Post
    I was asking because I thought it might be a failed check valve but if it's a 9 year old pump itself...I wouldn't totally discount that. Probably try to repeat the issue in the shop and check fuel pressures as well as voltage to the pump (rpm relay perhaps?) I'm just throwing out guesses.
    I drove it around, let it sit, and it did the crank, no start the 1st time, 2nd time cranking it started... so I started it a few more times, and it took longer than normal to start....
    also I remember the 1st all in one fuel pumps had a check valve issue, so a few years ago I installed a in-line check valve at the pump...

    Craig

  7. #7
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    could also be a loss of system pressure when the car is hot- at the primary pressure regulator in the Fuel distributor. if the little seals in there fail, then fuel pressure will bleed off. test fuel pressures and test for residual pressure after shut off, when hot, it should hold for about 30 min.

  8. #8
    Senior Member Silverbullet's Avatar
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    Quote Originally Posted by mark w View Post
    could also be a loss of system pressure when the car is hot- at the primary pressure regulator in the Fuel distributor. if the little seals in there fail, then fuel pressure will bleed off. test fuel pressures and test for residual pressure after shut off, when hot, it should hold for about 30 min.
    Ok,

    How is that done? Where do you hook up?

    Craig

  9. #9
    Motors about after dark Michael's Avatar
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    Quote Originally Posted by Silverbullet View Post
    Ok,

    How is that done? Where do you hook up?

    Craig
    The Primary Pressure Regulator is on the side of the fuel distributor. I think it's a 15mm? It is under sprung pressure so be sure to remove the last few threads by hand and a telescoping magnet wouldn't be a bad idea to get the final piece out.
    The O-ring kit is about 10 bucks and can be found at most all of the vendor's sites. Like I said earlier in the thread, it's hard to tell if they are damaged as just a small nick can cause a loss of rest pressure and usually if the rings are old, they are hard and brittle anyway so you destroy them just to check them.

    If they are more than 3 or 4 years old or you don't know, just replace them. It's cheap and easy.

    Last edited by Michael; 11-14-2021 at 09:34 PM.
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  10. #10
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by Michael View Post
    The Primary Pressure Regulator is on the side of the fuel distributor. I think it's a 15mm? It is under sprung pressure so be sure to remove the last few threads by hand and a telescoping magnet wouldn't be a bad idea to get the final piece out.
    The O-ring kit is about 10 bucks and can be found at most all of the vendor's sites.]
    A hint - when you remove and install this, if you have difficulty, remove the banjo bolts on the side of the fuel distributor. Actually you don't have to remove them, just back them off slightly. I've found that sometimes they go so far in they can hang up or nick the small o-ring. (Only one is really a problem but I forget which one.) Removing them all the way also gives you a place to carefully push it out or use compressed air. Don't go crazy with that or you'll be chasing parts all over the garage.
    Dave S
    DMC Midwest - retired but helping
    dswingle@DeLorean.com

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