Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
I imagine there was a typo and you meant this is actually a 6.6L. Do you have access to a capable scan tool to use for our diagnosis - Tech-II or equivalent?
I'm sorry, but, unless we're told up front, there is no way for us experts to know whether our customers are professional technicians looking for a little help, or DIY'ers who need a lot.
I'm sorry if I wasn't clear regarding the scan tool; I meant a scan tool equivalent to a Tech-II that could read engine and system data plus perform actuator tests, not just read codes. In this particular case, no-power on these LB7s usually means not enough diesel, so the first thing we would look at is MAF data.
I'm sorry, your reply came before I could post my response.
Please monitor what happens to the cam sensor signal once the engine warms up. In these engines, the onboard computer uses the crank sensor signal to start and run in basic mode; then, once the engine warms up, it looks to the cam sensor signals to fine tune injection.
If your scan tool can, please read injector on-time before and after warm-up to see if it changes in response to cam or engine temp signal.
Looking forward to your next reply...
The advantage of seeing the data on a scan tool is that it allows to identify and pinpoint the failure. Without that scan tool, we'd be basically left with process of elimination as the only recourse.
I did read the invoice from the repair shop. There was nothing in there that could help us diagnose the issue of no power after warm-up. Looks like we're back to scan tool or as you call it "shot gun trouble shooting"...
The way this injection system works, the onboard computer controls the injection pump as it meters, pressurizes and sends fuel to the eight nozzles.
I was hoping to see some kind of data showing how the system works when cold in comparison to how it works when warm. In other words, what changes from cold to hot that makes the engine run poorly. Is it metering, is it timing, etc.? Thing of it is, the only type of scan tool that I'm aware of that can "see" that kind of data is the Tech-II.
I'm sorry, but I only know how to diagnose these things using the right tools. I'll opt out and see if another expert can help you. Please don't reply until the other expert responds or the system will cycle it back to me.