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Thread: Ford 4.6 diagnosis, advice needed

  1. #1
    Member Rookie fscott's Avatar
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    Ford 4.6 diagnosis, advice needed

    I'm getting the Stang ready for Cresson, and I'm trying to figure out the issue that plagued me at MSRH a few weeks ago.

    I had some weird fuel pressure gauge issues that lead to me replacing the fuel pump and filter. Due to Ford's brilliant design, the pump is currently without a filter sock. The sock is lying in the bottom of the tank somewhere.
    As it turns out, the fuel pressure gauge was defective. A mechanical gauge shows no problems.

    After race 3, we went to impound. The car refused to start afterwards. I had to go out with my student, so didn't troubleshoot at all. I believe that Sook poked at it a bit. After the car had cooled, it started right up.
    On the out lap of race 4, the car was weak. It felt like misfires or a lean condition, I couldn't be sure which. I did the start to help with contingency, then brought it in. Unfortunately, the car idled well, and was only weak when under load. So short of driving it on the street and potentially getting arrested, I don't have a way to test it.

    Currently it's running fine. I've swapped out the cam and crank position sensors with some used spares. I don't know what else to try, but am open to suggestions.
    Last edited by fscott; 02-17-2022 at 06:13 PM.

  2. #2
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    my first thought is it sounds like possible vapor lock or I think the Fords have some fuel pump module or something like that. Does your fuel line get too close to any of the exhaust? Are you still running the relay module?

  3. #3
    This type of issue is tough because it's so difficult to diagnose on a track car.

    Back in 2018 I had an issue where my air filter failed and loaded the intake with rubber, causing high load loss of power. Started and drove around the paddock fine.

    Later in 2018 my fuel tank baffle broke off in tank and caused low fuel pressure in corners.

    Last year before Hallett, I had an issue with a cracked ceramic insulator on one spark plug that caused a high load loss of power. Again, started and drove around fine.

    Earlier this year, I had issues with my spark plug wires falling off on track. Lots of issues here.

    Michael had a fuel pump/regulator issue at Houston with similar symptoms.

    I think the sock being gone might contribute with low fuel, but it will definitely contribute in corners. I wouldn't necessarily rule out ignition either. One thing I've learned with track cars, is coincidence is pretty common.

    Josh
    CMC #50

  4. #4
    Senior Member Site AdminCarroll Shelby michaelmosty's Avatar
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    My first thought would be to do a new pump and sock as the old pump could be getting debris from the lack of a current sock. The strange thing is I wouldn’t think that would have an impact on whether the engine would refire after being at temperature.
    -Michael Mosty
    CMC #11 Mosty Brothers' Racing
    Director - TX Region

  5. #5
    Senior Member Carroll Shelby Supercharged111's Avatar
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    Really sounds like an electronic component failure. When they die, they tend to be happy cold and not hot. I forget what all is there to fail on the 4.6, were it a 5.0 I'd be looking at the TFI module.
    RM CMC Director

  6. #6
    Member Rookie fscott's Avatar
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    I threw on some spare crank and cam sensors. And I'm bringing a spare MAF this weekend. Those are the only things I can think of that would cause a no-start situation. Fingers crossed.

    Other components that I considered but rejected:
    Coil packs. There's two, so if one were bad I'd still have half of an engine.
    Coolant temperature sensor. Would make the car run badly, but wouldn't lead to a no-start.
    Air intake sensor is part of the MAF.
    MAP sensor - It doesn't have one.
    Last edited by fscott; 02-28-2022 at 08:52 AM.

  7. #7
    Member Rookie fscott's Avatar
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    Hopefully I've got it. Replaced the crank and cam sensors. Car worked for a bit, then stopped working. The pump ran but developed no fuel pressure.

    Dropped the tank, retrieved both socks, and refit the original pump with a new sock. All appears to be well now. But I'm bringing plenty of spares to ECR just in case.

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