12.7 Detroit backfires and throws fireballs

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Flipp, Apr 11, 2020.

  1. Flipp

    Flipp Bobtail Member

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  3. Flipp

    Flipp Bobtail Member

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    The problem ended up being the ecm? Was it a hardware problem or a software problem? That's the other thing I don't know is if the ecm is the problem could it just need to be turned or need to be replaced. I know that the ecm is factory tuned but turned all the way up to factory limits. I have wanted to get an aftermarket tune or somthing to get a little more power out of it but I don't want to turn up the power on an engine with problems.
     
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  4. Shawn2130

    Shawn2130 Heavy Load Member

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    Flipp: problem with the C15 is still unknown. Engine is currently being rebuilt as the head is cracked in 3 places.

    It is understandable how frustrating it can be trying to chase down problems and not even the Cat mechanics can find it. The computer says it’s running fine. Even brought a loaded trailer in for the test, drove for over an hour, when the problem shows up, it’s not showing on the Cat Et.

    So basically, we are at the throw parts at it stage.

    First we will see if the rebuild with a new head fixes the problem.
     
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  5. wtokhi

    wtokhi Light Load Member

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    im pretty sure the fact that the timing was off 1 tooth is ur reason, that always causes some sort of damage
     
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  6. Flipp

    Flipp Bobtail Member

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    It seems wired to me that it ran so smooth 1 tooth off. I have heard from others that it would barely run a tooth off, that's why I always wrote it off when people said I should check cam timing. Then after fixing it it runs the same. If there was damage as a result of being off a tooth Im guessing bent valves would be the expected damage, but bent valves would make it run like crap wouldn't it?
     
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  7. Shawn2130

    Shawn2130 Heavy Load Member

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    Flipp: any luck so far to solving the issue?
     
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  8. wtokhi

    wtokhi Light Load Member

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    i think it would depend on the severity of the bent valves, i came across a 60 that was two teeth off and it did run like crap and was sending pieces of valves through the exhaust, so one tooth it could still run, other than that it might just be an issue within the ecm
     
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  9. Rideandrepair

    Rideandrepair Road Train Member

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    When mine was overhauled, they found marks on 3 of the pistons from valves hitting. Don’t know for sure if or how bad the valves were bent. It wasn’t visible. They were probably that way for a while though. It ran good, up until I blew an injector, and eventually cracked the head. An Engineer from Detroit said it was probably caused by worn valve guides. Same mechanic found cam gear 1 tooth off on a friends 12.7, after he had bull gear done. Valves were bent, had to replace the head. I’m just guessing that the tolerances are so close, that a bent valve is possible.
     
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  10. Pete49dogs

    Pete49dogs Bobtail Member

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    Hey Flip you ever find your problem. I have the same issue. Driving me crazy..
     
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