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

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I have 2003 LB7 and have owned it since it was new. Now has 220,000 miles on it. Started smoking a little @ idle so just finished changing all injectors. Well, no more smoke or raw diesel smell from exhaust..... but truck continues to go ... JOIN NOW TO REMOVE TRACER

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  #1  
Old 04-18-2012, 12:47 AM
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Default Low rail pressure????

I have 2003 LB7 and have owned it since it was new. Now has 220,000 miles on it. Started smoking a little @ idle so just finished changing all injectors. Well, no more smoke or raw diesel smell from exhaust..... but truck continues to go into limp mode around 2000 rpm??? It was also doing this before injector change. Just changed fuel filter and it seemed to help a little. Now goes limp mode around 2700 rpm. Any suggestions????? Have changed fpr, think maybe time to change cp3 pump???? Had mechanic @ dealer check with tech II and it showed actual fuel pressure around 6000 psi even when command fuel pressure was 23,000. Please, any suggestions would be greatly appreciated!!!!
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  #2  
Old 04-18-2012, 01:27 AM
Diesel Bomber

   

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first off what codes are you getting?

the CP3 is a real possibility. did you try commanding max PSI while at idle?

it my also be the pressure relief valve, but that's not too common with the LB7s

if it is only getting 6000 PSI when commanding 23K it would run like crap and smoke a lot

2004LB7's Sig:2008 LMM Duramax 3500HD Dually
EFI Live, DPF fell off
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  #3  
Old 04-18-2012, 02:15 PM
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Default low rail pressure

Even in neutral, could not get actual pressure to go over 5700 to 6000 psi even when commanded to 23,000 psi. Truck does run like crap over 2700 rmp. Starts easy, hot or cold, every time. Just has no power. Once you get up to around 2700 rmp, its like hitting a wall. RPMs are up but its like it will not upshift until you let off the fuel. It also starts bellwoing out black smoke. Just put all new injectors in. Also change fuel filter, which helped a little bit. Was limping out @ 2100 rpm and since filter change, limps out @ 2700 rpm. Have also changed fuel pressure regulator. There's just not much left to change except for the CP3 pump ?????? Before changing injectors, when go into limp mode, would sometimes get code 1093 ?? Had dealer check, they said it was low rail pressure code.

Last edited by Harvey; 04-18-2012 at 02:17 PM.. Reason: incomplete
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  #4  
Old 04-18-2012, 04:41 PM
Diesel Bomber

   

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you could also try checking the return rate at the CP3. seems to me like it will be your CP3. did you make any changes to the trucks tuning before this happened? running any tuners?
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  #5  
Old 04-18-2012, 05:13 PM
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Default low rail pressure

Have been running a Bully Dog tuner since bought truck new in 2003. It has been set on 95 horse power tune since day one. Just run it for the fuel mileage. Never tow anything over 5000 lbs. I appreciate all of your input. Have been told by Brent @ Lincoln Diesel that it sounded like CP3 as well. Just wanted all the input I could get before cashing out on a cp3 pump. Eight new injectors and a cp3 pump in less than a week was not what I wanted to ever have to do
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  #6  
Old 04-18-2012, 05:38 PM
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just a thought, check for kinked or bent fuel lines on the supply (vacuum) side of the CP3
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  #7  
Old 04-18-2012, 05:42 PM
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Default low rail pressure

Yeah, unfortunately I have checked them and they all looked good. I was wishing that would be the problem as well.
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  #8  
Old 05-01-2012, 10:45 PM
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Well.....finally installed new cp3 pump. Everything runs great now!! Has plenty of power and pulls better than when it was new.
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  #9  
Old 05-02-2012, 10:31 AM
Diesel Bomber

   

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good to hear, glad you figured it out
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  #10  
Old 05-02-2012, 11:59 PM
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Hey thanks! Would also like to thank Brent Meyer @ lincolndiesel.webs.com for the injectors I installed. You could always call him at anytime during installation of injectors and he would offer great advise and answer any question you might have. Also, he had the best price for Bosch injectors I could find. Would also like to thanks rivercitydiesel.com for the Bosch CP3. They, too, had the best price for a Bosch CP3 I could find. Dieselbombers.com is a great site. First time I ever tried to install injectors or cp3. And with everyone's input from this site, it was not near as bad as I had as it seemed. I had been putting this off for about 1 year before finding all the great advice on this site. I could never see paying the dealer what they want to do this job. Again, thanks to everyone!
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