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Thread: Warm Start Issue - Resting Fuel Pressure Drops to 0 after 5 minutes

  1. #1
    Senior Member Nuclearbacon's Avatar
    Join Date:  Jun 2012

    Location:  Santa Cruz, Ca

    Posts:    209

    My VIN:    10588

    Club(s):   (NCDMC) (DCUK)

    Question Warm Start Issue - Resting Fuel Pressure Drops to 0 after 5 minutes

    Hello Everyone! Thank you for reading.

    My car usually cold starts no problem, and was warm starting perfectly. Back in 2010, the previous owner purchased a new fuel pump, and accumulator kit from DMC in Garden Grove (love those guys) and the cars been great until about a month ago. I'd drive it somewhere, park for an hour. When I'd get in, turn the key, the car would instantly fire up and die. Then I'd run the starter and run the starter and run the starter like the car had no spark. Checked my grounds. Found a loose ground under the ballast resisters and one on the frame rail. Still issues after tightening. Cleaned up the connections on the ballast resisters. Finally decided to get in and check the fuel pressure. I'm losing fuel pressure after the car is turned off.

    After hooking up a fuel pressure gauge, I found the rest pressure drops to 0 from about 3.75 bar within 4 minutes. The shop that is helping me specializes in the Bosch K Jetronic system which is really cool. It's nice to have someone looking over my shoulder who seems to know the system pretty well as I'm just learning it as I go along.

    In September of 2010 the car had a new fuel pump and accumulator installed along with a whole o-ring fuel kit sold from DMC garden grove. Everything I'm reading says my accumulator is no good, but it should be new-ish still right? Could my accumulator be bad after only 4-5 years and less than 7000 miles?

    I also found this: http://support.delorean.com/KB/a61/h...rt-issues.aspx

    Looking at the my previous invoice I mentioned above, I wanted to make sure I didn't have an older style fuel pump as mentioned in the website. I believe my fuel pump is a newer style. The shop thinks that the fuel pressure is being leaked into the cylinders causing a flooding issue. or instead of it leaking into the cylinders, could it be losing pressure through the o-ring the site above mentions at the end? The shop seems to think the system pressure regulator o-ring is the culprit. They also want to pull my injectors to inspect.

    What would you do? What do you think it is?

    Thank you!


    -Luigi-
    Thank you ALL for your patience and your tremendous help!

    1982 VIN#10588 Build Date Dec '81

  2. #2
    Senior Member hmcelraft's Avatar
    Join Date:  Jun 2011

    Location:  McKinney, TX

    Posts:    234

    So, why don't you trust the mechanics? Specialists should be able to test it readily - especially if they have the gauges and all the accessories to test the system? The O ring sounds like as good a place to start as any. Fuel pressure dropping very fast as in your case is a major leak-down. They will be able to determine the fault quickly I suspect. The O ring is cheaper than the fuel accumulator and much less labor cost. If you have the mechanic isolate the accumulator to test it you may as well replace it and get your labor money's worth. If by chance the replaced accumulator you mention was NOS (new old stock and 30 years old) it could have failed after little use because of poor storage over the years, etc.

    Don't forget there is a backflow valve at the fuel pump that can go bad also. The newer style fuel pump just not as often (or rarely).

  3. #3
    Senior Member Nuclearbacon's Avatar
    Join Date:  Jun 2012

    Location:  Santa Cruz, Ca

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    My VIN:    10588

    Club(s):   (NCDMC) (DCUK)

    I do trust them! I was just curious since I have the weekend before I can place the order, I'd just ask!
    -Luigi-
    Thank you ALL for your patience and your tremendous help!

    1982 VIN#10588 Build Date Dec '81

  4. #4
    One of those purists you keep hearing about. sdg3205's Avatar
    Join Date:  May 2011

    Location:  Vancouver, BC

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    My VIN:    thirty two 'o five

    Club(s):   (PNDC)

    The areas of warm start issues:

    1. Accumulator - remove rear hose and check it holds 20 in Hg vacuum

    2. PPR - 3 possible o rings can be faulty. Inspect.

    3. CSV - prime system and inspect for leak

    4. Injectors - prime system and inspect for leaks

    5. Pump check valve - pinch send hose after priming and see if rest pressure holds.
    Dave

    Here, somewhere.


  5. #5
    Junior Member
    Join Date:  May 2012

    Posts:    11

    I was having the same hot start issue, after replacing everything. I found out it was the check valve within the brand new fuel pump/sender unit had failed. So when the car is shut down, you lose all your fuel pressure back into the tank.
    I proved this by using the fuel pressure gauge on the engine and then pinching the fuel line near the pump and the pressure remained high once the engine was shut down. The easy solution was to put an after market in line check valve just after the fuel pump.

  6. #6
    Senior Member Nuclearbacon's Avatar
    Join Date:  Jun 2012

    Location:  Santa Cruz, Ca

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    My VIN:    10588

    Club(s):   (NCDMC) (DCUK)

    Thank you for the replies!

    Update!

    Got ahold of DMC in LA, asked about my fuel pump to see if it was the older style mentioned above with the questionable valve, and my series was one of them. So I
    purchased my own K Jetronic Fuel Pressure Test Kit. Got it this morning and went out, hooked it up and recreated my drop in fuel pressure after reaching operating temperature almost exactly 4 minutes to 0psi. Repressured the system, turned the car off, went to the front of the car and pinched off the supply line from the fuel pump and still had a drop in pressure. Seems my check valve isn't the issue.

    Time to start at the beginning for MYSELF. The shop said they tested my accumulator. I am going to grab a vacuum gauge tomorrow and get under the car and see if I have the 20"Hg with my own two eyes. If I do, I continue onwards.

    SO nice to have the fuel pressure kit. I highly recommend it, as other have recommended it to me. I'm also ordering Dave's solid state relay as a gift to my car when I figure out the starting issue.

    Onto Vacuum testing!
    -Luigi-
    Thank you ALL for your patience and your tremendous help!

    1982 VIN#10588 Build Date Dec '81

  7. #7
    Senior Member Bitsyncmaster's Avatar
    Join Date:  May 2011

    Location:  Leonardtown, MD

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    My VIN:    03572

    Replacing the PPR o-ring is a 5 min job, so that's what I always do first.

    I have seen a few NOS accumulators fail with very little time in use.
    Dave M vin 03572
    http://dm-eng.weebly.com/

  8. #8
    LS Swapper Josh's Avatar
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    Location:  Illinois

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    Club(s):   (DMWC) (TXDMC) (DCUK) (DOI)

    I had a rest pressure issue. Turned out to be the elbow that screws into the bottom of the fuel filter!

    Supercharged 5.3L LS4 + Porsche 6spd
    [email protected]
    lsdelorean.com
    I am not affiliated with Delorean Midwest in anyway.

  9. #9
    Senior Member Nuclearbacon's Avatar
    Join Date:  Jun 2012

    Location:  Santa Cruz, Ca

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    My VIN:    10588

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    Defective vacuum gauge. Sonofa.....
    -Luigi-
    Thank you ALL for your patience and your tremendous help!

    1982 VIN#10588 Build Date Dec '81

  10. #10
    One of those purists you keep hearing about. sdg3205's Avatar
    Join Date:  May 2011

    Location:  Vancouver, BC

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    Quote Originally Posted by Nuclearbacon View Post
    Defective vacuum gauge. Sonofa.....
    ?


    Sent from my iPhone using Tapatalk
    Dave

    Here, somewhere.


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