LLY: Lly knock with white smoke

[00f3fiddy]

Truck has 280k miles on it. Has a skip and a knock. Sounds like fuel knock to me. Blows white smoke out of exhaust and smells strong of fuel. I can disable a inj with a snap on solus ultra and stop the knock but the smoke never clears. I installed a fresh set of reman Bosch injs(from a very reputable shop) and still have the problem. I ran a compression test and its 380 on the lowest to 470 on the highest. I haven't checked balance rates because I don't let it run long enough to build any temp. Any ideas? Possible bad inj or base engine problems? I would think base engine problems would have shown up in the compression test!! Any info would help!
Thanks

 

[TexasRob]

380 to 470 seems like a big spread to me on compression test. Sounds like head gaskets

 

[00f3fiddy]

Most are 400-420. I can disable #4 inj and stop the knock. Compression on it is 450. #8 is the lowest at 380. No fuel in oil either or puking from coolant reservoir.

 

[TexasRob]

Honestly Im not the right person to take advise from on Duramax motors. I just know that getting a variance of 90psi on a compression test isn't a good thing on most motors.

 

[00f3fiddy]

Any other ideas?

 

[02greysixer]

450, 470 is to high. You have to disable the fuel while doing the compression test. Did you unplug the ficm while testing? I'd be willing to bet you have an injector(s) hanging. Try swapping injectors 4 and another easy one to get to and see if the problem follows the injector.

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[00f3fiddy]

Injs have 0 miles on them. Ficm was unplugged for compression test. I guess it is possible to get a bad inj out of the box.

 

[02greysixer]

Yeah I'd start rearranging injectors to see if the problem follows the injector. If you have an injector leaking it'll give an artificially high compression reading.

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[00f3fiddy]

Thanks for the info!

 

[00f3fiddy]

Thanks for the info!

 

[00f3fiddy]

Got to work in this some today. Cold start up #8 balance rate is +15 then drops to +6(cold) #8 was also the lowest in compression @380 others 400-475. I used my bore scope and tried to look at # 8. It's sooted up so bad can't really tell much. Can see a light spray pattern but nothing just sticks out. I moved injs around and it stayed on #8. It's weird as the knock sometime is very faint and others very loud. I can disable #4 sometimes and it gets very faint, sometimes it never changes. Guess I need to pull the valve cover off and see if there is any valvetrain damage.

 

[dracing70]

How is the injector harness to number 8? Maybe u have a bad connection there on that cylinder?? Usually it's 2 or 7 that has harness problems but it could b a possibility. Maybe u should go the pick fix on that plug.

 

[00f3fiddy]

Forgot to list it has a new engine harness on it

 

[00f3fiddy]

.

This is what I saw on my bore scope looking through #4 inj hole! I took a pic of the screen so clarity kinda sucks! Looks like I need to pull the head see what happened.

 

[00f3fiddy]

I snatched the airbox out while pulling the engine and found this! I think this could be the root of the problem. Turbo is dusted too!

 

[dirty_max]

oh boy, thats no good. plan on an overhaul

 

[andy-stevenson]

What's in the picture of the borescope?

 

[00f3fiddy]

What's in the picture of the borescope?

Debris.

 

[00f3fiddy]

Found the knock. #8 piston has some extra travel and twist!