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

just a usless update the dealer replaced a whole lots of parts still havnt fixed it. have to get the parts list the guy paid a couple g's fopr the parts so he bitched about it till they gave him back all his money cause one of the workers screwed up and said you did need that.
another story another friend custom ordered a 2500 crew cab with a dirtymax only to have simular problem again the dealer replaced all the parts they could still wouldnt fix it they had to buy back his truck and give him another

what about crank or cam sensors? if the timing was being thrown way off would it do this and not set any codes?

have to see if they replaced them. it would only do it maybe once a day and only happen when leaving from a stop like a stop light ot stop sign.

map sensor issue .. it sounds like ... i been reading more on these exact issues.. might be able to clean ir up and or have to reaplce it .. :tu:
can u scan for that ?