LMM stand alone fail

[Mogman]

Well I was showing my wife's boss the Duramax/Humvee and the last thing I heard when I left was "get on it" so I did but quickly came upon a RR crossing that was pretty rough so I shut it down and was braking as I past over the tracks, all was OK until I tried to accelerate on the other side of the tracks, there was a total loss of power above idle and it was running very rough and smoking, please do not laugh but the best I can describe the sound was YIP,YIP,YIP,YIP......

There was no indication of mechanical failure, (valves hitting pistons, rod hanging out of the side of the block ETC.) so I shut it down and had it towed home.

When it was warm it would start as I just pulled it to the shop as far as I could and just ran it long enough to get it in the shop (hard to push a vehicle with an aluminum body and no bumper)

Now that it is cold it does not want to start, just smoke, BUT the cylinder compression seems to be even while cranking and I pulled the oil fill cap and it is not puffing out of there so I do not think I have a cylinder/piston/valve failure.

I am not sure where to go from here... there are no codes or MIL

 

[Bdsankey]

Can you take a datalog? It may tell you more than a quick snapshot on a diagnostic device screen.

 

[Mogman]

Can you take a datalog? It may tell you more than a quick snapshot on a diagnostic device screen.

I have no idea how to do that, I will try and research it, do you mean while I am trying to start it?

 

[08lmm72mm]

Hows the crank? Watch the HB while trying to start it.

 

[Bdsankey]

I have no idea how to do that, I will try and research it, do you mean while I am trying to start it?

Do you have an EFILive autocal at all? And yes, while cranking. A good scanner should be able to help you diagnose it but it can be difficult at times to watch all the PIDs on one screen while cranking etc.

 

[Mogman]

Yes I do have EFILive, will try and get that set up, I have some chores to do first, might be tomorrow, I see 50Mpa fuel pressure during cranking., dropping to 45-47 on the odd occasion it tries to fire, will look at the crank when the wife gets home and she can crank it.

 

[Mogman]

This morning I turned off the batteries and re-seated the connectors on the ECM, she started up and ran rough for a few seconds, cleared up and seems to be as good as new, I must have shaken one of the connectors loose on the RR tracks (the smaller one did not look fully seated)

HOORAY!!!

I have actually been putting off trouble shooting for fear of the worst case scenario, looks like a beach run tomorrow!!!
Thanks to all that responded!!!!!!!

 

[Mogman]

This brings up a question, I am missing one of the "bales" (the blue part that folds over and locks the connector) on one of the engine to body harness connectors, I believe they are both the same, is this a part that can be purchased separately? I am using tie wraps to hold it together now...

 

[TheBac]

I don't think so.....but you could go shopping at the local boneyard, or someone here may have one. That's probably your rough running issue right there. I once left one loose, and going down the road the truck started running like crap. Thought, uh oh. Locked that connector back down and no issues. The Electronics are very sensitive to connector issues.

 

[Ron Nielson]

Zip ties work. May need more than 1.

 

[Mogman]

I did not make it out of the gate Sunday, I was opening the gate and she started to sound a little "raspy", withing a few seconds it was back to the YIT, YIT, YIT.
I suspect another broken wire at one of the ECM connectors. The ECM was flung around pretty badly during the donor truck roll over and I already found one wire pulled out of the pin on one of the ECM connectors, at least that time I had a code to follow,,,,,

 

[Mogman]

I have cleaned all the connections with a little Deoxit and so far it is 99.9% better, I cannot really determine if the exhaust sounds different or if it is my imagination, it also seems like the turbo opens up to the "LBZ" setting faster than before when started cold, but no smoke and she idles smooth and responds to the accelerator well.

So if I run a log what perimeters are important to have in the log?

I have low expectations that what I have done has "fixed" the problem or if it is possibly an intermittent mechanical issue (injector?) that just SEEMS to be responding to what I am doing but in fact is just random...