buddy's LMM is hurt

[N2BRK]

Long story short - helped my best friend build up his truck. We got her tuned and on the test drive she went boom. Truck stalled and fuel everywhere. White smoke fills the sky.

Flatbed. Parking lot thrash. #5 injector pissing fuel out the bore. Removed and resealed injector. No joy. Put in old shelf-aged core. Leak gone but smoking at cold idle badly. Reprogrammed injector... maybe a RCH better but not great. Balance rates on that cyl and opposing bank not happy. No excessive blowby. No rock hard hoses. Warmed up and driving she's good. Traveled home 10hrs just fine except for cold start.

Back home - New injectors. Cyl 5 still upset. Cold smokes like a filthy whore. Balance rates in neutral +6.8 on cyl 5. In gear drops to 1.0. Injector 6 seems to be compensating as it's showing -3.6 in gear and -4.0 in park. All others are under 1.0.

He went to work yesterday and did a compression test - all cyls over 400psi. He tried to borescope but it was too dirty to see anything.

I was thinking he hurt a rod but the compression was good. Unless that's something that can be slightly hurt and not affect compression but still act this way?

Electrical gremlin? Seems like a pipe dream that nothing is physically hurt on this engine, but it's been thrown out there.

Some armchair diag help would be nice, please TNX - Wally

P.S. I'd be remiss if I didn't say that Larry and Mark were a godsend out there in IN. Larry flatbedded us back ASAP and Mark lent advice, tools, and help when we got back to the shop. These are some great guys! WKS

 

[2004LB7]

Swap injectors to a different cylinder. See if the problem follows. Turn off injectors and see if the smoke goes away

Even if it had a slightly bent rod, the compression is what is going to make the difference. And since it is good I doubt that is your issue. I would make sure you have a known good injector in it and electrical/wiring is good

 

[Chevy1925]

does the cold start smell like fuel?

only way it will do that is from a bent rod or injector that is way over fueling. wouldnt hurt to check the front for a wobbly balancer too (broke crank) but it may be back farther at the cyl 5 journal.

 

[N2BRK]

I questioned him on wiring, and when we talked last night he was going to starting ohming it out.

It's had three injectors in it, including new Bosch from Lincoln. No change. He said he unplugged the injector and the truck ran better. No smoke nor rough idle.

 

[N2BRK]

does the cold start smell like fuel?

only way it will do that is from a bent rod or injector that is way over fueling. wouldnt hurt to check the front for a wobbly balancer too (broke crank) but it may be back farther at the cyl 5 journal.

Thanks. I was convinced of a bent rod, but his compression test told me that I was wrong. We can check for a broken crank next. I dismissed that early on, but maybe foolishly so. Thanks

 

[2004LB7]

I questioned him on wiring, and when we talked last night he was going to starting ohming it out.

It's had three injectors in it, including new Bosch from Lincoln. No change. He said he unplugged the injector and the truck ran better. No smoke nor rough idle.

Wouldn't unplugging an injector disable the whole bank, meaning 4 injectors will be disabled?

 

[N2BRK]

checked with him on phone - he unplugged the injector. Truck ran much better.

 

[N2BRK]

on phone - morning white smoke smells like fuel.

 

[Chevy1925]

Wouldn't unplugging an injector disable the whole bank, meaning 4 injectors will be disabled?

not on LBZ and up IIRC


N2BRK
What is the actual compression per cyl?

 

[N2BRK]

James - I called him and he said he did it on a warm engine, by himself and didn’t write the numbers down. All were within 10psi and about 400psi. I’m going there Sat AM to redo it together. But that’s all I have for now. Thank you !

 

[2004LB7]

not on LBZ and up IIRC


N2BRK
What is the actual compression per cyl?

Good to know

 

[gmduramax]

Bent pushrod maybe?

 

[N2BRK]

I suggested that yesterday to him and he didn’t think so, but now he’s willing to consider anything. I stopped off here to his house tonight. Doesn’t have the compression tester from work avail until Saturday. He started it and it’s a white train of smoke. Pull the #5 wire and no smoke and the lope and misfire sound goes away.

 

[gmduramax]

You have a video of the sound?

 

[NC-smokinlmm]

Have you reloaded the tune? Or run the stock tune? Maybe you have a bad ecm or the tune is wonky.

 

[N2BRK]

I’ll get video.

Yes, reloaded the tune last night. No change.

 

[N2BRK]

Oh, also... does the DVT tool in Efi live not shut off injectors on the LMM? Last night I was using it to shut them off one by one and it did nothing. Other functions worked fine, idle or rp manipulation for example.

 

[Bdsankey]

If compression is good and unplugging cyl 5 injector makes the smoke/lope go away then I'd lean towards either a bad injector/wiring somehow causing it to not do what its told. One would imagine a bent pushrod would show up during compression. Possible leakdown problem?

 

[N2BRK]

Not that I don't trust his skills, or claim to be anything more than a glorified shadetree mechanic, but I want to do the compression test on Saturday myself and then share the data. Ideally a leakdown test too.

 

[2004LB7]

Oh, also... does the DVT tool in Efi live not shut off injectors on the LMM? Last night I was using it to shut them off one by one and it did nothing. Other functions worked fine, idle or rp manipulation for example.

Works fine for mine. Every once in a while it doesn't respond and turning dvt controls off and on again seems to correct it. Also I think it is mapped to the firing order and not injector number or something like that. I don't think the labeling matches the injector numbers