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Thread: $EE '94 Fbody Manual not starting, logs attached

  1. #1
    Electronic Ignition!
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    $EE '94 Fbody Manual not starting, logs attached

    Hi all, i need some help. Engine in questin is 94 Corvette LT1 with LT4 Hot Cam Kit and equal length tri-Y headers, adapted to Audi 6 speed manual, installed in the backseat of a 1965 Corvair. C4 harness pared down to stand-alone, $EE 8051 PCM, bin based on the latest 94 F Body Manual. On 11/22 I drained the water from my cooling system and refilled with 50/50. Freezing temps on their way (Detroit area). With the bleeder open on the thermostat housing, a stream of 50/50 peed onto the Opti connector. Did not try to start the car until 11/24, and it wouldn't start. I noticed Vbatt falling off, and she set DTC 16 Low Res Fault, which I've seen other times when Vbatt got around 10V or maybe a little less. This evening, 11/25, i pulled the Opti connector and shot it with WD40, blew it out with compressed air, gave it a little dielectric grease, and reconnected. The DTC 16 was still present from not being cleared on 11/24, so I cleared it before attempting to start. Again, crank crank crank but no start. I noticed INJ PWs were really long, but i don't know what's "normal" because this is the first time i've tried to start it with CLT and IAT around 5 deg C. Again it set the DTC 16, again after cranking for several seconds and Vbatt dropped a bit. I pulled the spark plugs and all were wet with fuel. I don't know whether to believe i have an Opti problem, or if my cranking fuel is way off for this cam and these temps, and my Vbatt dropping is causing the DTC 16. I'd greatly appreciate if y'all could have a look at the .eedata logs and the .bin in the attached zip file and let me know your thoughts.

    Thanks a lot!
    Patrick aka AngryCorvair
    Attached Files Attached Files

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  3. #3
    Electronic Ignition!
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    Quote Originally Posted by steveo View Post
    it needs a low res pulse to start
    do you own or can borrow an oscilloscope?
    thanks for the reply, steveo.

    i should have noted that the car was starting normally and driving pretty well until this. I know that doesn't mean the Opti isn't dead now.

    i have a pocket scope that i bought a couple years ago. does the Opti have to be removed for this, or is it done on-car? sorry, i'm sure the procedure is in the FSM, which i have in the house somewhere.
    Last edited by AngryCorvair; 11-26-2023 at 10:51 PM. Reason: additional info

  4. #4
    LT1 specialist steveo's Avatar
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    while you crank the car do you get any rpm or injector pulsewidth in the datalog
    you scope the opti in the car i just use a pierce probe and a two channel scope and crank the car over
    the high res pulse looks like a fast uniform pulse width and low res is uniform interval but varying pulse width (cyl id)

  5. #5
    LT1 specialist steveo's Avatar
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    oh and unlike newer ecms that have a backup cyl id strategy this ecm simply will not spark or spray fuel with no low res pulse

  6. #6
    Electronic Ignition!
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    Quote Originally Posted by steveo View Post
    while you crank the car do you get any rpm or injector pulsewidth in the datalog
    Yes, INJ PW and RPM are both present.

  7. #7
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    Years ago coolant in the opti was considered leading cause of death. I've disassembled opti then cleaned and dried everything inside and sometimes found success. Most times not. Maybe folks have new strategies? A test for spark is still a test for spark so I'd include that along with diagnosis by datastream.

    Hope you get it sorted. Sounds like a fun ride.

  8. #8
    LT1 specialist steveo's Avatar
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    if you have injector pulse and fuel pressure and spark it'll start or at least sound like its almost going to start.
    you're missing one of those things figure out which
    if your opti is dead your injector pulse and spark will both be gone

  9. #9
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    I’m hoping to get back into the garage tomorrow after work. Thanks for the pointers, I’ll update when I dig in again.

  10. #10
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    Starter shaft broke right at the nose bushing. Never seen that happen before. Anyway, thatís fixed and she still didnít want to start. INJ PW in the 70 ms range? Held pedal at WOT for flood clear and she started after a couple seconds of cranking. I havenít made any changes from stock for cranking INJ PW so not sure why sheís spraying so much fuel. Anyway, it seems like the Opti was not the problem. I will play with reducing cold cranking enrichment and report back if I make any breakthrough.

  11. #11
    Fuel Injected! MO LS Noobie's Avatar
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    I would look at your ECT. See what temperature your PCM thinks the engine is. Open circuit will show -40 degrees F. Will flood engine immediately. Bad crank position sensor can cause kickback breaking starter or even engine blocks.

  12. #12
    Electronic Ignition!
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    Good suggestion, thanks! Both ECT and IAT are present and behaving normally. I'll continue to go through my logs, as well as look at all the cranking PW contributors via TunerPro.

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