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Thread: Powerdyne FMU to Fuel Rail Question

  1. #26
    niebs's Avatar
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    How long after start up are those? It takes a ~30 seconds for the o2s to turn on and start adjusting fuel.

    But those trims indicate a rich condition which is in line with the coil failure fault. And bc both banks are rich, so the code is for your main coil.

    STFT B1S1 - Short Term Fuel Trim Bank 1 Sensor 1. Basically is what the front o2 is seeing and correcting right now.

    STFT B1S2 - Is the o2 after the cat. Which should that high if the cats are working.

    LTFT - Long Term Fuel Trim - If the STFT Sensor 1 is always adding or pulling fuel then it will remember it and add that into the fuel map as a base. (Kinda anyways. not sure how else to explain it) But the fact that is says zero just means that the computer has been reset and you have not run it long enough for that calculation.

  2. #27

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    I get po351 ,no check engine light. Always thought that was caused by the msd 6 and msd coil.fuel trims says rich conditions PCM I is lowering pulse width by those percents . Fuel pressure may be too high or map sensor signal is incorrect . Try anther map sensor hose location.

  3. #28

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    Have you double / triple checked everything. Wiring damaged, connectors connected tight. Correct firing order on the cap and wires. Grounds. Wiring is getting old and crispy. Put mine together this spring with new fuel rails and thought I had had everything connected, ran like shit and it ended up being that I didn't seat the MAP sensor connector.
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  4. #29

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    I think evil offers good advice.

    P0351 is from the MSD for the coil not reaching max. dwell time.
    Nothing to be concerned about. Anyway, check your 02 sensor fuses. You may have a bad o2 or a wire has come off or melted.

    I also have the MSD 6 box and coil. I even replaced the MSD coil and still get the code. There seems to be an incompatibility w MSD and stock pcm. My AFR seems ok at idle and elsewhere.

    Your problem sounds electrical to me like a crossed wire or bad connection. Other possibility is a fuel sync being off if you inadvertently moved the distributor..
    If you go back to everything stock as far as coil and ignition (if you still have those pieces), you can begin to narrow it down.
    If you had a vacuum leak that bad, it would throw a code for such like a P 0451, P 01494 or similar.

    I am not a fan of computers and sensors they decided to put in cars back in the 70's as a bunch of kids were coming out of college with computer degrees.
    I also hate this day light savings time shit.
    Last edited by arro222; 11-10-2021 at 01:12 PM.

  5. #30
    TC-RT's Avatar
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    Thanks for all the help.

    Below is an update:

    I checked all wiring I could get my hands, nothing loose or disconnected.

    Firing order of plug wires is correct on distributor cap to the plugs.

    I replaced both left and right upstream o2 sensors.

    I disconnected the MSD and blaster coil. Reinstalled OEM coil.

    Its runs a bit better, but still rough.

    I took it for a drive not getting into the throttle.

    Got to 60 mph, check engine light started flashing.

    Got home and hooked up the scanner, got a #5 and #8 cylinder misfire.

    Pulled the #5 wire from the cap while running, no change in idle, ran the same.

    Reconnected #5 and pulled #8 wire from cap while running, no change in idle, ran the same

    By this time it was too dark out to go any further.

    Will try some more troubleshooting another day.

    Thanks again.
    Terry

  6. #31

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    if you are 100% sure that the firing order is correct, start the engine and let it idle to warm up. using a spray bottle of water, spray each header tube and verify no sizzle on the 5 & 8 tubes and sizzle on the rest. once verified, swap the injector from each of those cylinders to one that did produce water sizzle and then retest. you may have a bad or clogged injectors.


    a compression test might be a good idea, but it seems like that should not be an issue.
    1941 Dodge 1/2 ton, 493 twin turbo, EFI, 727, 4 wheel disc brakes, custom triangulated 4 link, DANA 60, Gleason Torsen diff,

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    1998 Dakota RC daily driver 5.9L, AX-15 5 speed, Hooker long tube headers, FRP tune

  7. #32
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    Put a spare plug in #5 plug wire and ground it out while running. See if it arcs. Then do the same with #8.
    If no spark then I would swap with one of the wires that is known good and see if it arcs in #5 or 8 location.
    If no spark again, then pull the cap and see whats up.

  8. #33
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    @wedged and Niebs

    Thanks for the advice.

    I started by using my infrared thermometer and #5 and #8 were running cooler than the rest.

    This morning, I decided to do what Niebs suggested with an extra plug. Long story short, an arc was shooting out the side of the plug wires #5 & #8 from underneath my heat wrap around the wires.

    The result, bad plug wires. These were new wires I had stored in a temp controlled environment for a couple years. I never thought to pull off the heat wrap to check the wires.

    What could cause this to happen? Maybe the wires had some dry rot from sitting?

    Anyway, gotta get new wires now.

    Thanks again for all of your help.

    20211125_124638.jpg

    20211125_124755.jpg

  9. #34

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    looks like it burned from laying against a header tube.
    1941 Dodge 1/2 ton, 493 twin turbo, EFI, 727, 4 wheel disc brakes, custom triangulated 4 link, DANA 60, Gleason Torsen diff,

    2002 Dakota R/T RC, PX8, PPH Headers, K&N FIPK, Hotchkis TVS, 20" R/T chrome rims, BFG G-Force T/A KDW 275/35 ZR20 tires, Kenwood head unit, Kenwood speakers, RF amp, 8" RF Punch Z subs

    1998 Dakota RC daily driver 5.9L, AX-15 5 speed, Hooker long tube headers, FRP tune

  10. #35
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    I just saw the up date on this. Glad you got it sorted out!
    Remember that the arc will find its least resistance to ground. So bad fuel or poor plug will make the arc find the weakness link. Could be a small dry rotted crack in the wire. It happens.

  11. #36
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    (dbl post)

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