Duramax fuel system vrs Cummins

[Andres]

I have a friend with a transplanted DMax. He's experiencing loss of power and hard starting, and intermittent dying. No codes. To me is sounds like bad fuel.



My understanding is (probably not correct) that the Duramax uses a Bosch CP3 and no lift pump. I know there have been iterations of the basic motor over time. Being a V design, I assume that it has a couple of fuel rails, connected with a single rail pressure sensor and pressure relief valve? Or is there a single rail in the valley? I beleive the injectors are of a similiar Bosch design as ours.



Finally, if it uses a CP3 without a lift pump, what gives? Oh, and what to check besides fuel delivery and quality?



Slightly off topic, but I had a similar problem with my CTD and 30 gallons of algae infested fuel.



Thanks

 

['strokeThis_'07]

My understanding is (probably not correct) that the Duramax uses a Bosch CP3 and no lift pump. I know there have been iterations of the basic motor over time. Being a V design, I assume that it has a couple of fuel rails, connected with a single rail pressure sensor and pressure relief valve?

This is correct



Whats it swapped into? What year DMax? I havent enough exposure to a Duramax to help much, but I know the injectors are an issue on earlier years.

 

[cerberusiam]

Curious as to why the CP3 on the DMax doesn't need an LP.

Bigger lines, less restriction, different tank to pump location are the main reason they don't have one stock.



Saying they don't need an LP is a stretch. Even stock systems seem to benfit from the inline pusher pumps they install.



Check fuel, injectors, IP in that order.

 

[Matt400]

Also GM has been having issues with clogged and weak injectors, wonder how many miles the transplant has on it? If it needs injectors better sit down first.

 

[Tinman]

The Jeep Liberty CRD with the VM Motori 2. 8 uses a CP3 with no lift pump. I put in a Faceut lift pump last year but I'm gonna replace it with my 06 in tank pump I'm gonna use the libby's canister the my truck so I can run it less that 1/4 tank without the aftermarket lift pump sucking air.

 

[Wingate]

Glad you got it fixed... Its my understanding that the CP3 on the DM is a 3 stage pump. The first stage sucks the fuel from the tank, thru the fuel filter base and charges the second stage of the CP3. Our field service trucks are DM engines and they have proven to be anything BUT reliable or durable. We have had a range of issues from simple codes that de-fuel the engine, H2O pump failures, injection pump failures, fuel filter base failures, injector failures beyond belief, charging system failures, and total engine failures that seem to come at the 70K to 80K mile ranges... We have yet to get one to make 100K.

I really think GM should have kept these engines in 1-ton and below trucks. . In that application, they fare pretty well. But, when in a 1 1/4-1 1/2 ton that is always loaded, I personally think the engine is too light weight of a design to endure the constant strain. It seems that our failure rate supports my thoughts also. .

 

[Tinman]

That's the 6. 6 your talking about, right? Not the 7. 8? I've always wondered how the bigger Duramax was doing.