Need advice on 03 duramax fuel system

jaybird1ton

jaybird1ton

The Flats Offroad Park
Joined
Sep 11, 2008
Location
Marion
Either my cp3 pump is going bad or my fuel pressure regulator. I don't know much about this and could use some advice on how to trouble shoot. I also have a ppe lift pump. Call if you have any advice...thanks 828-442-7932
 
my aftermarket lift pump went out and now my truck is not running good. It will run for awhile then start running bad. Is my cp3 pump going bad or is it bad?
 
define "running bad"

the OEM fuel system SUCKS fuel from the tank, your pump pushes it, if your add on pump isn't supplying the needed volume it is now an obstruction in the system, causing greater resistance for the CP3 to draw.

Fuel filter(s), new? clean ? seated properly ? bleed screw on filter housing tight, not cracked ? WIF sensor on bottom of filter fit properly ?

LB7 is known for injector issues, any fuel in the oil ? has it set any codes ? if an injector is bypassing, it will cause overall fuel pressure to drop, which could act like a fuel pressure regulator problem.

Need a scan tool to see actual and commanded fuel pressures, if it will reach 23000 psi when commanded, but then it drops off suddenly, yes, then I might suspect FPR or even the injection pump, but there are several other things it could be.
 
jaybird1ton said:
my aftermarket lift pump went out and now my truck is not running good. It will run for awhile then start running bad. Is my cp3 pump going bad or is it bad?
Click to expand...
Takes a good bit of work to determine that. The big questions are 1: have you replaced the faulty lift pump? 2: when the trucks running poorly is there an indication of a faulty pump (low rail pressure, low rail pressure codes, stalling etc)? 3: when you say running bad what do you mean, smoke or no smoke? Noise or no noise? Low power? Surging? 4: any specs from the truck such as balance rates, delivery rates, return rates, actual and desired rail pressures, pressure or vacuum numbers at the test port.
Considering it happened directly after a lift pump issue I'd look at the suction side prior to jumping to conclusions. What type of lift pump was it? If there is no filtration between the lift pump and cp3 a faulty lift pump could send debris into the cp3. No way to even guess at the cause.
If you do have a code, look for a freeze frame and that'll save you data logging sessions just trying to make it act up.
 
Lift pump is a ppe 160. It went out completely. Won't even run if it hooked straight to the battery. So that left me running with just the cp3 pump.
No smoke. I can still drive it Just runs kinda crappy and once and a while will just shut off. Kinda like the cp3 is losing pressure and maybe the lift pump was helping it but when the pump went out then the cp3 isn't putting out enough pressure alone? Is there any way to clean the cp3 out from debris without taking it out. It sounds like that is a job to do.
 
No cel isn't an indication of no code. Might start there. Sounds like the lift pump is still in line, if so you must take it out. We can guess all the day long, but without a scan tool and some data from the truck that's all it'll be. Guessing. If the lift pump isn't in line, I'd look at fuel restriction. It's possible it could be the cause of the lift pump failure.
The cp3 can't be cleaned or serviced by diyer (some minor performance work can be done but nothing that's capable of repairing your issue). It'll need to be sent in for a rebuild if that's the case.
 
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