My beloved Duramax needs help.

[jjeff]

Yes I'm aware of the dreaded cp4 pump issues. however my issues started after I stubbornly asked them to replace fuel filter which was due for service but running great beforehand, when the belt,idlers, and tensioner was replaced so it makes me think it's something with the fuel filter hopefully. I'm aware of several aftermarket fixes to prolong the life of the cp4. One even mitigates damage to injectors if the pump grenades so a several thousand dollar job, doesn't cost 10k. I'm not for taking it in to get fixed, certainly not over 500 miles away.

 

[Like Tractors]

Trifecta - Bad fuel, fuel filter woes, injector pump failure

Everything is computerized and you need the dealer. I don't miss my Duramax, especially out of warranty issues

The smart money says if you are going to own a late model diesel pick up, buy it new and get rid of it before the warranty is out. Or buy old ones that have positive pressure to the high pressure fuel pump. All Duramax equipped pick ups prior to 2017 model year have no supply pump and the high pressure pump has to draw fuel from the tank, which puts the system under a negative pressure from the fuel tank to the inlet of the high pressure pump.

 

[Hay Dude]

Wonder why CP-3’s don’t self destruct under negative fuel pressures.

 

[Like Tractors]

Wonder why CP-3’s don’t self destruct under negative fuel pressures.

If you saw the internal parts of the two different pumps, you would no why, the 3 cylinder CP-3 is very tough. The 2 cylinder CP-4 has little piss ant rollers that are approximately 0.375" in diameter that run against a two lobe cam, the wear starts very early in life for those pumps, hence the statement "they start grinding themselves up from the first time you start them".

 

[Hay Dude]

Why in the world would anyone build a newer pump that goes backwards in reliability?

 

[mikester]

Why in the world would anyone build a newer pump that goes backwards in reliability?

That's what happens when bean counters make decisions and overrule engineers.

 

[jjeff]

In my pessimistic worst case scenario feel the system wasn't bled properly at least to the filter so if the cp4 pump is failing I'm imagining the hard starting issues initially were caused by sucking air there by further or ultimately damaging an already weak high pressure cp4 pump. This is getting out of my wheelhouse as im only somewhat capable of successfully diagnosing and repairing smaller old yanmar and universal auxiliary diesel sailboat engines occasionally a 40 yr old Kubota tractor but rarely have to.

 

[Hay Dude]

Yeah, but Bosch?
Pretty good company.

Kind of makes you wonder if the CP4 is up to the task with lots of input pressure?

 

[Hay Dude]

In my pessimistic worst case scenario feel the system wasn't bled properly at least to the filter so if the cp4 pump is failing I'm imagining the hard starting issues initially were caused by sucking air there by further or ultimately damaging an already weak high pressure cp4 pump. This is getting out of my wheelhouse as im only somewhat capable of successfully diagnosing and repairing smaller old yanmar and universal auxiliary diesel sailboat engines occasionally a 40 yr old Kubota tractor but rarely have to.

Don’t go “worst case scenario” on us. Just try the cheap things first. 9 out of 10 times, thats the issue.

 

[YanmarFever]

Im going with the improperly installed fuel filter, and there is air in the lines or pump.
Like Hay Dude says (its the cheap little things) that need to be tended to first.