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Thread: Stumped with fuel delivery problem.

  1. #1
    Senior Member 3yearplan's Avatar
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    Stumped with fuel delivery problem.

    The drivetrain is 2004 Mach 1, DOHC 32V, Mustang fuel tank, pump etc. Here is the dilemma: Turning the key to the on/acc position the fuel pump will come on, pressurize the system and stop, like it normally would. Turn the key to the crank position and the vehicle will start, but the fuel pump will NOT kick back on, therefore the engine only runs for a few seconds. Changed out the fuel pump, fuel pump control module, the crank trigger sensor. Double and triple checked wiring, matches up with the schematics from the Mustang, have plenty of ground wires that have also been triple checked. The computer was flashed by Ron Francis to ONLY remove the PATS and after cat O2 sensors. ANY help or information is appreciated. This has been going on for far too long. I prefer to keep this set up, but if I can't figure it out I'll be forced to get a complete new fuel system, which I don't want to do. Had it hooked up to a Ford dealer scan tool, no codes came up.

    Thanks, Mike
    Last edited by 3yearplan; 12-06-2017 at 12:48 PM.
    Mark IV 7923 arrived 11-14-12
    DOHC 4.6L, Tremec 3650, 3 Link 8.8 w/3.73

  2. #2
    Steve >> aka: GoDadGo GoDadGo's Avatar
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    Mike,

    Could the culprit possibly be an issue with the inertia switch?
    It's that goofy looking thing up by the main wiring harness with the big Red Rubber Button with the mounting tabs on each side.

    Steve

  3. #3
    Senior Member Straversi's Avatar
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    I chased fuel pump wiring problems and finally got the electrical correct but still wouldn't start. Discovered the fuel pick up hose had slipped off. Fixed that and it would start but then quickly died. I assumed it was still fuel pump related but found out I had my MAF sensor in backwards. Flipped it and runs like a champ
    MK IV #8901 - Complete kit, Coyote, TKO-600, IRS. Ordered 5/23/16, Delivered 7/14/16, First Start 8/13/17, First Go-Kart 10/22/17. Build Thread: http://thefactoryfiveforum.com/showt...V-Coyote-Build

  4. #4
    Senior Member 3yearplan's Avatar
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    I will certainly check both of those items. ALL ideas are appreciated.
    Mark IV 7923 arrived 11-14-12
    DOHC 4.6L, Tremec 3650, 3 Link 8.8 w/3.73

  5. #5
    Am I understanding correctly that when you go from ON to CRANK the fuel pump doesn't kick back on? If so, what happens when you go from OFF to CRANK? Does fuel pump come on and stay on?


    John
    MK IV Roadster #8631
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  6. #6
    Do you have a pressure gauge on the fuel line so that you can verify what the fuel pressure is doing

    The pressure may not have dropped to a level that would cause the pump to turn on


    Rick
    #8475 Complete Kit Delivered Nov 2014, started Nov 2015, Street Legal Apr 2016, Paint and Interior Completed Aug 2017, 390FE, March accessory kit, MSD Atomic EFI and Ready to run, TKO 500 with MidShift kit, hooker headers, 3 link, track lock with 3.55

  7. #7
    Senior Member Big Blocker's Avatar
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    So what you're saying is; Fuel pump comes on at initial start sequence, turning the key to ON, you get a single pulse to the pump (normal). Then when you crank the engine over, there is NO fuel pump function (I believe that's normal). Then when the key is returned to ON to keep the engine running, there is no fuel pump function? How am I doing so far??

    To the best of my knowledge, The fuel pump needs to "see" the engine [actually] running and that function is controlled by the crank trigger. Once the engine is spinning, the pickup at the crank trigger constantly re-triggers the fuel pump to cycle again and again.
    If possible, check your wiring at the crank trigger to ensure that the trigger pulses are in fact happening - sounds like they are if the engine will run until the fuel pressure drops off to a point where the engine won't continue. That being said, you may be getting the trigger pulses for ignition but not the fuel pump, causing the pump to NOT run.

    IF the inertia switch was bad, you wouldn't get the initial pump run cycle, it's in series to the power lead to the pump. It's either open or closed, not intermittent.

    If your fuel pump runs and gets to design pressure, it's not the fuel pump.

    HTH

    Doc
    Last edited by Big Blocker; 12-06-2017 at 07:12 PM.
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  8. #8
    East Coast Speed Machines Erik W. Treves's Avatar
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    This a classic run and stop with PATS still enabled... could be that while you asked for it to be disabled it isnt.
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  9. #9
    Senior Member 3yearplan's Avatar
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    Gentlemen, I have no idea how to do the "quotes" thing. So I'll answer in order:

    John, It will come on just for an instant and when the engine fires it will not come back on.

    Rick, the initial pressure is at 45-47 psi, after it starts it will slowly drop and the engine will die.

    Doc, first paragraph, yes, yes, and yes. I'll double check the wiring at the crank trigger pickup. Hmmm how could I get a crank trigger pulse for ignition, but not the pump? I've eliminated the fuel pump as the issue, put in two different ones. We have wired the fuel pump to run constantly to eliminate it. The engine runs fine that way. I know the factory pump is not designed for that type of operation, it was just a trial of two-three minutes.

    Erik, how would I actually test to see if the PATS is actually disabled ?


    Thanks again, this forum is invaluable for things like this. Unfortunately I don't have the "normal" engine to help out that many people.

    Thanks again, Mike
    Mark IV 7923 arrived 11-14-12
    DOHC 4.6L, Tremec 3650, 3 Link 8.8 w/3.73

  10. #10
    I have a PATS disabled car here I am working on. I believe its a 99 Computer and harness. When PATS is active, it kills the injector power too. Maybe this is specific to this year, but something to look into on yours. Sounds like you have injector power.
    Mike

  11. #11
    Senior Member 3yearplan's Avatar
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    Thanks Mike, I'll add it to the checklist.

    Thanks again, Mike.
    Mark IV 7923 arrived 11-14-12
    DOHC 4.6L, Tremec 3650, 3 Link 8.8 w/3.73

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