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Thread: ECU failure?

  1. #1

    Default ECU failure?

    So today after setting valve lash and changing transmission fluid, the car will not stay running. Starts & idles like always than after about a minute, bam, shuts off and reprimes the system. Software shows ECU lost connection. It did this 4 times and now I can't even connect to the ECU via software. Just looks like it doesn't even see the ECU, although car will still start off of the ECU. I got a datalog of it, but it stops when the ECU shuts down. Up to that point everything looks typical. All connections are tight with no changes and battery voltage is 14V while running. I'm fearing the ECU is intermittently failing causing it to die momentarily, and restart as it acts like I cut the key off & on really quick. Just started doing this, so I'm kind of clueless. I'm running all my relays off of a clean distribution block. The factory ignition hot connection triggers a relay, which allows for battery voltage to feed the distribution block. I'm not seeing a power loss anywhere else but the Sniper. Out of ideas and frustrated cause I also found a brand new lifter that is soft. When it rains it pours.

  2. #2
    Join Date
    Dec 2009
    Location
    Connecticut
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    19,295

    Default

    This seems like it's losing the RPM signal and causing the ECU to reset itself.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  3. #3

    Default

    How would I check that? I'm running the dual sync distributor & coil driver.
    What really concerns me is that EFI software will no longer connect to the ECU after it did this three or four times.
    Danny, if it was losing RPM signal, I should see a drop in RPM before the system restarted and cut off the datalog correct?

  4. #4
    Join Date
    Dec 2009
    Location
    Connecticut
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    Default

    When the engine doesn't start, does the Data Monitor display legitimate cranking RPM?
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  5. #5

    Default

    The engine starts. The faults I'm experiencing are that the engine suddenly dies and immediately primes.
    It did this 3 or 4 times after restarting and now the Sniper EFI software won't even connect to the ECU.
    I managed to get a datalog of it suddenly shutting off and back on, and there's no drop in RPM signal or any other value when it shuts down. It's weird.

  6. #6
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    19,295

    Default

    So it's probably not the RPM signal. As a test, you could temporarily connect the switched +12V red/white wire (pink wire - Sniper EFI) directly to the fully charged battery's positive terminal.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  7. #7

    Default

    OK I'll try that, thanks.

    I hooked a multimeter to the Sniper EFI ignition hot wire, and didn't notice any voltage drop at the power wire when the Sniper EFI shuts down. I'll still try a direct battery connection to all the Sniper ignition hot connections and see what happens. It did allow me to connect EFI software to the ECU today. Weird part is that it dies sooner the colder it is. After several restarts when the engine bay warms up slightly it stays running longer, still ultimately dies but does run longer. It's like the ECU is being troubled by being 30°F.

    UPDATE: OK, connected distribution block to battery directly. The distribution block feeds all the Holley stuff. Does exactly the same as before. Runs for anywhere between 5 & 60 seconds and shuts off, and immediately reprimes like ECU lost power.

  8. #8

    Default

    Sounds similar to the issues I was having with the dual sync & coil driver. This is a short video of mine at startup/run/die. Watch till the end. On the 2nd start it run for a bit then goes crazy & dies again. I put my HEI back in and it runs way better. Little stumble and lean spikes on deceleration. Working on that now. https://photos.app.goo.gl/pKovfRyEGSIU2Ctk1

  9. #9

    Default

    Ben Barron yours is doing some things mine is not. Mine runs totally fine with all sensors good & clean, and shuts off instantly & reprimes. My TPS doesn't fluctuate, RPM stays steady, AFR stays steady, just shuts off & back on.

  10. #10

    Default

    Check all wires, especially power, key on & RPM signal. This sounds like losing power or RPM signal.

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