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Fuel pressure loss when hot?

Discussion in 'Engine/Tuning' started by Pantera1, Sep 15, 2019.

  1. Pantera1

    Pantera1 Member Established Member

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    When the car is at operating temp (15 minutes on the highway) and just cruising the car will randomly stop accelerating. If I tap the gas pedal itll sputter and go back to the power loss. If I turn the key and bump the starter itll drive normal again for a minute before losing power again. I've gotten it to do it at idle a few times and my fuel pressure gauge on my regulator reads 0 and will idle bad before eventually killing itself. My tuner says it looks like the ecu just freaks out right before it happens. Car has gen 4 whipple, also did id1050x, aem 320 pumps and new lines at the same time.
    Does anyone have any leads on where to look?

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  2. railroad

    railroad Well-Known Member Established Member

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    Fuel pump relays?
     
  3. wkornf

    wkornf Member Established Member

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    for what it's worth I had similar issue and it was the pump. however it's just as likely anything electrical upstream. do some diagnosis



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  4. slo984now

    slo984now AKA 01yellerCobra Established Member

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    Sounds like a problem I had with my AEM pumps. But my issue was at WOT. At part throttle it was fine. I could watch the fuel pressure drop when I punched it. Turned out one of the pumps went bad. I thought I could use them in a returnless set up, but that wasn't the case.
     
  5. P49Y-CY

    P49Y-CY selfie deaths ftw Established Member

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    i think I have the same problem, the car only shuts down after it runs for about a half hour or so.
     
  6. Pantera1

    Pantera1 Member Established Member

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    That's exactly what's going on

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  7. P49Y-CY

    P49Y-CY selfie deaths ftw Established Member

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    in my case i have another identical car that i have been able to swap parts with and so far i have tried just about everything except the fuel pumps... injectors, cop's, maf, tb, fpdm, frps, etc.

    i am now in the process of dropping the fuel tank to check it out. my car has 126k and still has the stock eaton.

    (i understand that the better, more professional way to diagnose this kind of problem would be to datalog and scan different parameters, but i am not too good with computers and swapping these parts has not cost me any money)

    edit: it is not my pumps, and since your pumps are new op i doubt that they will be the problem in your case either. did your tuner say anything else other than your ecu "freaks out"? it is a very strange issue - in my case the car runs fine for about a half hour each time before stalling.
     
    Last edited: Sep 22, 2019
  8. Pantera1

    Pantera1 Member Established Member

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    That all he said to me. My car runs fine for 20-30 minutes then dies randomly

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  9. MG0h3

    MG0h3 Premium Member Premium Member Established Member Established Member

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    Could be vapor lock.

    Go pull the cap after it happens and see if you get a big woosh of air.

    If you could log you could monitor FPDC when this is happening.

    ECM failure is incredibly rare.


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  10. P49Y-CY

    P49Y-CY selfie deaths ftw Established Member

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    well if i figure out my issue i'll def let you know! our problems sound very similar. mine is very consistent... it runs for almost exactly 30 minutes (give or take 5 minutes) each time. very weird!
     
  11. Wings65288

    Wings65288 Well-Known Member Established Member

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    Do you guys have a deadhead fuel setup or flow-through?
     
  12. Pantera1

    Pantera1 Member Established Member

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    Mine is return style

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  13. Pantera1

    Pantera1 Member Established Member

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    I had read something that said maybe having the regulator exposed in the engine bay may introduce too much heat to the fuel system, maybe that's my problem

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  14. MG0h3

    MG0h3 Premium Member Premium Member Established Member Established Member

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    Doubtful. All foxes had it. Plenty of Cobra guys run that way. Possible that the pumps are going out and the heat adds load and they don’t like it.


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  15. MG0h3

    MG0h3 Premium Member Premium Member Established Member Established Member

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    Did you delete the Evap system by any chance?


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  16. Pantera1

    Pantera1 Member Established Member

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    I did not, alsobtheyre brand new aem pumps
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  17. slo984now

    slo984now AKA 01yellerCobra Established Member

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    But are you running it dead head or flow through. I have my return style set up as dead head because it was easier to plumb.
     
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  18. Wings65288

    Wings65288 Well-Known Member Established Member

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    Yeah I've heard flow through is better for preventing vapor lock. Thats what im going with. Just a thought.
     
  19. Pantera1

    Pantera1 Member Established Member

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    I believe it would be flow through. Pump to back of rails, front of rails to regulator and back to the pump

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  20. Wings65288

    Wings65288 Well-Known Member Established Member

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