Chevy/GMC Duramax 01-04 LB7 Discussion of Chevy and GMC Trucks with LB7 Duramax Turbo Diesel Engines

02 lb7 fuel problems

Old Jun 24, 2015 | 10:33 AM
  #21  
kestmic1's Avatar
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Cutting out at high rpm caused truck to go into limp,Lifter tick, blow haze of smoke when i reved it up in higher rpm .Could not even do a brake torque.
 
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Old Jun 24, 2015 | 10:36 AM
  #22  
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bad fuel pressure regulators will usually cause fluctuations in the fuel pressure. if bad enough it can be felt at idle. when cruising down the road it will usually be masked by the constant fluctuations of the pressure anyways.

if it is real bad it can prevent the pressure from reaching it's desired set point. this is not as common, at that point the CP3 is probably worn too and cant build pressure.
 
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Old Jun 24, 2015 | 10:40 AM
  #23  
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Originally Posted by kestmic1
Cutting out at high rpm caused truck to go into limp,Lifter tick, blow haze of smoke when i reved it up in higher rpm .Could not even do a brake torque.
sounds like real low fuel pressure coupled with limp mode fuel restrictions.
 
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Old Jun 24, 2015 | 10:47 AM
  #24  
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Originally Posted by 2004LB7
sounds like real low fuel pressure coupled with limp mode fuel restrictions.
These symptoms I had when fpr was bad that I explained. Replaced the cp3 with new one before that ran fine after that. My buddy's truck is acting just like Gillespie is explaining and he replaced cp3 3 weeks ago had injectors checked I think the cp3 came with new fpr to.
 
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Old Jun 24, 2015 | 11:26 AM
  #25  
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yes, new CP3s come with a FPR
 
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Old Jun 24, 2015 | 11:37 AM
  #26  
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Originally Posted by 2004LB7
yes, new CP3s come with a FPR
His truck ran good for about 10 mins after putting on cp3 and fpr but then it just started all these other problems.
 
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Old Jun 24, 2015 | 12:15 PM
  #27  
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i was off a little on rpms i cked this am .according to this chart ,pressures are ok , i think i have a bad new injector .
 
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Old Jun 24, 2015 | 05:40 PM
  #28  
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Originally Posted by gillespie3033
i think i have a bad new injector .
it is not common but it happens. more often it is problems with assembly as getting contaminants in the lines or injector(s) while it is open. very important that everything stays real clean. new injectors can go bad real fast with just a little bit of grit or rust getting into them
 
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Old Jun 24, 2015 | 09:20 PM
  #29  
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Default lb7 low fuel pressure

The problem you describe is likely to be a bad fuel pressure relief or overflow valve located in the valley of the engine, follow the fuel return line from the passenger side head to a junction block in the valley the so called relief valve is actually a pressure regulator which limits fuel return to the tank and handles excess pressure(over 25K psi) from the CP3 pump which is also t-ed into the junction. The relief valve is spring loaded and can be disassembled, and is probably rusted and pitted since water in the fuel will collect there, you can only buy a new one from Bosch, there are some after market "plugs" available but they might be risky for a daily driver. let me know if this solves your problem.
Rich
 
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Old Jun 25, 2015 | 03:51 PM
  #30  
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okay we will check that out. thanks
 
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