duramax smoking problem
 

this is for a friend, he has had the injectors replaced a few months ago due to fuel in the oil. now not all the time but from time to time when he comes to a stop he will try to take off and blow black smoke and no power. took it to the dealer they replaced the GP module for some reason no cel or problem starting. other details about the truck idk lol im pretty sure its a lb7 due to the injector problems and early 2000s. doesn't do it all the time and no other problems, any questions ask. sorry for the lack of info

low fuel pressure can cause that ..... filter issues ?

any stumbling when its doin this ?

it goes no where. the guy says i moves slower than walking, and it only does it at a intersection. i read that a injector could be returning too much fuel and cause the low pressure, but how does low pressure cause black smoke?

if its returning too much fuel it would barly fire injector .... like running lean , it would sound almost like a ping.

the fact that it only does it at stoped ... thinking fcim not getting or sending enough volts @idle maybe ???

check injector wiring ( use ohms and to test from end to end , contunuity would be good to do a shake test to see if cont. stops when shaken ) ...

keep posted , could also be a weak CP3, low fuel pressure causing low or dribbling fuel spray pattern as well , causing fuel to puddle on top of the piston ?? hmmmmm ...

i know you don't know what motor or year it is, but if it's newer with the vgt turbo and the turbo is sticking all the way open it will cause this. It's just like trying to spool a big single. i saw a 6.7 cummins that did this every once in a while. Being as it's not all the time i'm inclined to throw out a weak cp3 or injector problem.

from memory i want to say my bud said it didnt have a wastegate but worked some other way. and it did act like (to him) that the waist gate was open

i would say:

MAF issues, clean and/or replace or

Boost leak, should be easy to tell as it will normally hiss or squeal but not always. check for loose boots or holes rubbed through boost lines, or

possibly a bad turbo. check for play in the turbo shaft and for smoothness in rotation.

Also, double check for stored codes if there is no CEL.

low fuel pressure will cause a CEL (unless it has been disabled by a custom tune) so it wouldn't be my first guess.

dealer replaced maf and glow plug part (cant thing of the name). turbo had no play. the dealer hooked up a "black box" for codes and nothing has popped up yet. dont even know if it has reoccurred yet.

huh ... anything latley ?

havnt talk/seen to the guy since last post. ill ask around and see what anyone has heard