LB7: Rough Idle with White Smoke (Injector or Cracked Piston)

[Sandracer799]

Driving up the road today I accelerate onto the interstate like normal. I look behind me and I see white smoke. I pull over. The truck is idling rough, white bluish smoke, some oil and smoke is coming out the breather tube, and has a raw fuel smell to it.

I have put my EFI scan tool on it, but I am not 100% sure I know what I am doing.

Cylinders 1 -3 stayed at -7 to -7 the entire time I recorded.
Cylinder 4 was 4.77 to 4.85
Cylinder 5 was -7 to -7
Cylinder 6 was -6.63 to -6.54
Cylinder 7 was -7 to -7
Cylinder 8 was 15 to 15.


Am I just a moron and not doing this right or is this the real readings? If so is 7 injectors bad? (Not within the +4 to-4 spec at idle)

Any help at all would have been greatly appreciated!!

 

[catman3126]

sounds like you have a bad injector filling the crankcase with fuel

 

[DIESELMAFIAPER.LB7]

sounds like you popped a piston take the oil fill off and see if it is puffing alot of white smoke

 

[catman3126]

how full is you crankcase with oil/fuel?

 

[catman3126]

sounds like you popped a piston take the oil fill off and see if it is puffing alot of white smoke

Yeah if he has alot of blowby like a puff puff puff then for sure hope its just an injector though

 

[Sandracer799]

There is no fuel in the crankcase.

 

[Sandracer799]

It is puff puff puff out of the oil fill.

 

[catman3126]

broke piston first sounding like you had raw fuel coming out of the vent but yeah if its not burning it in a cylinder there will be fuel vapor coming out. bummer man sorry bout your luck

 

[DIESELMAFIAPER.LB7]

It is puff puff puff out of the oil fill.

Sorry to hear man but you lost a piston from what your saying

 

[Burn Down]

Looks like more than just a cracked piston... Looks like there may be some shortened rods and some injectors on there way out as well. Have you checked the balance rates before?

 

[dracing70]

I have 7 low mileage lb7 pistons if interested. About 60000 on them and rods

 

[jraymer]

Hold down or hold down bold broken? I have seen a hold down bolt break and cause the same symptoms.

 

[Sandracer799]

Would the cracked piston cause the readings I am getting for the injectors or do I have multiple problems??

 

[chevyburnout1]

If one cylinder is misfiring badly it will cause erratic readings for the other cylinders as well. Sounds like something happened in the #8 cylinder. Those were close to the same readings I had when I bent my #8 connecting rod.

 

[catman3126]

Low compression in a cylinder will cause strange balance rate readings. the computer is trying to compensate for the lack of return it wants to see from that cylinder so it will try to inject more fuel to keep the rpms steady. if one cylinder is not doing its job then the computer will try to compensate to pick up the slack from a low compression cylinder wether it be come bent rod or a piston that has too much blowby

 

[DIESELMAFIAPER.LB7]

i have a bent rod my balance rates look fine lol

 

[paint94979]

Have you ran a lot of nitrous through the engine?

 

[catman3126]

I see how do you know you have a bent rod then? not being a smart as just curious?

 

[paint94979]

I see how do you know you have a bent rod then? not being a smart as just curious?

I'm sure he did a compression test

 

[catman3126]

well yeah but a comp test does not automatically mean a bent rod, could be valves not sealing could be score cylinder wall. cracked piston