8.1L shutdown

[Timberline]

I have a freind that has a 2500 ext cab with an 8.1L / Allison.

The problem is the engine will shut down on it's own but all of the accessories wil stay on. When he puts the truck in nuetral or he gets it to stop he can hit the ignition and it will fire back up. He has cleaned the battery posts and even installed a new battery and it still does it.

Anyone heard of anything like this before?

[madmatt]

what year? any codes? If no codes I'd suspect the PCM is losing voltage on the IGN1 circuit. Also I'd check ground G103 @ the left rear of the engine block.

[Timberline]

It is a 2002, no codes at first but the check engine light did finally come on. He has dropped it by the dealer so not sure what the codes are at this time.
Your thoughts look dead on. I had mentioned to him about the ground but I had no idea where to start looking for it.

[madmatt]

does the engine die as if someone turned the key off or does it diesel and chuggle to a stop? Will it do it every time he drives it or after any certain run time? It's hard to diag something like this over the PC due to the numerous possibilities of symptoms and conditions. it could have a plugged cat. converter, bad ignition switch, weak fuel pump relay, weak fuel pump, plugged fuel filter, bad PCM ground circuit, bad PCM supply circuit, bad PCM, etc, etc...

[madmatt]

also there are no bulletins on it.

[Timberline]

Turned out to be the crank trigger for the ignition failed.

Like you said there are a million different things that could have happened to make the truck die.

[madmatt]

I've replaced those before but for different concerns. Mainly rough idle on cold start. Those things are a pain in the a55! 6 inches long. on the back of the engine, and under the cab for the most part. I really love it when independant shops break'em off in there then have them towed in :mad: !!!