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Discussion Starter · #1 ·
Hey I know this is a long shot but I have a problem with my lb7 that I can't figure out the problem to I've researched alot and can't seem to find the problem so instead of taking my truck to the dealer I thought I'd reach out to you.... I haven't driven the truck in a while but I went to start it the other day and it was cranking and cranking but wouldn't start then I primed the fuel and it started then as I was driving it it seemed to be rolling alot more coal then its supposed to but it was black smoke coming out the exhaust not white or blue it was black. Then I got home and at idle it wasn't hazing or smoking at all but it was knocking pretty good sounded like the duramax tick but louder. Then I put it in drive and as soon as I would touch the gas it would instantly roll coal no matter how much throttle I put into it. But again when I put it in park no haze or anything then I shut it off and it won't start again just cranks over. I was thinking injectors maybe but normally injectors have a white haze at idle and idle rough when my truck wasn't at all. No engine codes or anything so that leads me to believe maybe it was a boost leak but would that affect it not wanting to start? Let me know please and thanks if you have any ideas on what the problem may be it would be greatly appreciated!
 

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Check airbox for rodents? They like to make their home in the air filter. If filter is clogged less air = more smoke?
 

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Discussion Starter · #3 ·
Check airbox for rodents? They like to make their home in the air filter. If filter is clogged less air = more smoke?
I will check that forsure still doesn't explain why I had to prime fuel the other day to get it to start but could be a problem. Thanks
 

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I could be mistaken but, to roll coal means too much fuel. So is that a FPR? Im not positive, If it was a boost leak it would be loud and a distinctive sound you wouldnt miss.
 

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Discussion Starter · #6 ·
I could be mistaken but, to roll coal means too much fuel. So is that a FPR? Im not positive, If it was a boost leak it would be loud and a distinctive sound you wouldnt miss.
I'm not familiar with FPR. I do indeed think it is a stuck open injector tho not a boost leak anymore. I will look into FPR tho thanks for the feedback
 

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I'm not familiar with FPR. I do indeed think it is a stuck open injector tho not a boost leak anymore. I will look into FPR tho thanks for the feedback
Im not familiar with fuel problems. Although i have replaced injectors. Ive never had a fuel problem other than that.
 

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Fuel Pressure Regulator shouldn't cause it to dump fuel into the cylinders and roll smoke though. If the intake tract is clear, given the injector knock, my assumption would be a stuck open injector. I have run into some rare instances when debris has caused an injector to not fully close causing a fuel knock and heavy smoke. A couple times, a good hard romp on the throttle has raised the fuel pressure enough to blow out the debris and the injector then operates normally. The times I have seen this, normally the high pressure lines have been off and the rust/corrosion has not been fully cleaned out of the injectors or lines and then gets into the nozzle and hangs it open. Worth a shot, but don't run it like that too long- if it does not clear out by doing this, and it is a bad injector that is stuck open, it can tear up the engine in a hurry too
 
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Discussion Starter · #9 ·
Fuel Pressure Regulator shouldn't cause it to dump fuel into the cylinders and roll smoke though. If the intake tract is clear, given the injector knock, my assumption would be a stuck open injector. I have run into some rare instances when debris has caused an injector to not fully close causing a fuel knock and heavy smoke. A couple times, a good hard romp on the throttle has raised the fuel pressure enough to blow out the debris and the injector then operates normally. The times I have seen this, normally the high pressure lines have been off and the rust/corrosion has not been fully cleaned out of the injectors or lines and then gets into the nozzle and hangs it open. Worth a shot, but don't run it like that too long- if it does not clear out by doing this, and it is a bad injector that is stuck open, it can tear up the engine in a hurry too
Okay thank you very much I will try this out
 

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Fuel Pressure Regulator shouldn't cause it to dump fuel into the cylinders and roll smoke though. If the intake tract is clear, given the injector knock, my assumption would be a stuck open injector. I have run into some rare instances when debris has caused an injector to not fully close causing a fuel knock and heavy smoke. A couple times, a good hard romp on the throttle has raised the fuel pressure enough to blow out the debris and the injector then operates normally. The times I have seen this, normally the high pressure lines have been off and the rust/corrosion has not been fully cleaned out of the injectors or lines and then gets into the nozzle and hangs it open. Worth a shot, but don't run it like that too long- if it does not clear out by doing this, and it is a bad injector that is stuck open, it can tear up the engine in a hurry too
Thanks DMAX. As i stated before never have i had an issue with this. Thanks again for the input
 

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2003 GMC 2500HD 4x4 Banks Super Scoop, Banks Rear Dif Cover, Mechman 320A alternator, S&B fuel tank
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If a stuck injector is potentially the issue would it be worthwhile to do the GM injector cleaning process?
 

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2003 GMC 2500HD 4x4 Banks Super Scoop, Banks Rear Dif Cover, Mechman 320A alternator, S&B fuel tank
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I'm by no means an expert, but worst case it wouldn't hurt anything would it?
 

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Wish I had more to add, good luck!
 
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