LML CP4 Problems

[Janimal444]

I did some searching and found some information on this but did not find a thread dedicated to this subject. I have heard claims of failed CP4s wreaking havoc on the entire fuel system. Basically I am wondering the following:

-How exaggerated are these claims? does anyone have any firsthand experience with this happening or know of anyone who has experienced this issue.
-What causes this issue. I have heard that the current ultra low sulfur diesel has a lubricity which is lower than what is recommended by Bosch to run through their CP4 pump, is this true?
-What can be done to rectify this problem? (Lift pump, aux. filter, additive etc.)

Since I'm in the market for an LML I'm just starting to do some research on these trucks, this is the only thing I saw which really stood out at me.

 

[hondarider552]

only thing that can be fixed with that issue is swapping in a CP3 kit. IIRC I think Fleece has converted one, not sure. As far as first hand experience, I have none, but on duramax forum, there is 5-7 guys that have posted about their failed engines.

 

[Janimal444]

I wonder if they were stock trucks or tuned? In other words does a tune starve the CP4 and worsen the issue?

 

[Dirtymaxx03]

I believe it has something to do with what the plungers inside the pump are made of.

The ceramic plungers inside the injection pump of one of our 450ISX Cummins exploded and took out the whole motor.

 

[ryan415]

We've had a few trucks with cp4 failures and have ended up replacing the entire fuel system. Trucks are 100% stock. Iirc it's due to the ceramic plungers as Dirtymaxx already said. I know fleece and maybe also wehrli make a cp3 conversion kit.

 

[02greysixer]

We've seen it go both ways. One bone stock Duramax got by with just a new pump. The other two I remember were 6.7 Powerstrokes and they had to have complete systems done.

 

[S Phinney]

It definitely is the ceramic parts that cause the catastrophic failures of the system.

 

[Big Block 88]

Over 50k on ours still going strong no issues. One trip towing heavy with it you will be in love. All trucks have there issues, and I feel the cp4 claims are exaggerated, you only hear about people posting the bad stuff, no one posts about about thousands of trouble free miles

 

[gmac32]

I replaced a friend of mines entire fuel system because of the cp4. It had a little over 100k on it and out of warranty. I tore the pump apart and saw the bores were all scarred up and one plunger wouldn't even move. The rollers on the bottom of t!he plungers had complete flat spots in them to where they wouldn't even ride on the cp4 cam right. Junk Pumps period!

 

[Independent03]

Put me on the list. I've got a 2015 with 17k and the pump went out 1000 miles from home. All stock. Needs a whole new fuel system. Dealer said it could be two weeks. Not happy.

 

[NC-smokinlmm]

Dam it.. I thought gm fixed that issuse...

 

[Max Attitude]

Why did they go to a CP4? Is it just bigger? Every time I read about this it makes me nervous about my inlaws LML that I tuned.

 

[islandgirl62]

My 2012 took a dump on me, going 80 mph down the interstate in Wyoming, with 77,000 miles on it. (H&S Street Tune, FASS lift pump, cold air induction and 4" exhaust) A big shudder, dash flashed "Change Fuel Filter" then "Engine Power Reduced". Coasted to the exit ramp (fortunately it was MY exit!) that's when I realized the truck had completely shut down because I didn't have power steering anymore. Threw 7 codes, the first of which was Low fuel rail pressure. Most of the rest had to do with the truck having shut down and still moving faster than the CPU thought it should be moving. FASS filters had metal shavings in them. Factory filter had metal shavings in it. Still wouldn't start. Put it on a hook and took it to a diesel shop. Bottom line - they told me there is a service bulletin from GM on it. And the whole fuel system has to be replaced. (I have a copy of part of the bulletin where it mentions having to replace the whole fuel system if metal shavings are found.) So I'll have new everything, rails, injectors, pump, fuel lines, high pressure lines, etc. I asked the mechanic specifically and he said I have a CP3, not a CP4. That was a bit confusing because I'd been told by others that the 2012's all have CP4s. It's gonna cost me plenty to have it fixed. I didn't find out about the service bulletin until it was well into the tear-it-apart stages trying to find what all was damaged when the pump went out so don't know if I'll have a chance at getting anything back from GM for the repairs. Up until this happened, the truck was running like a champ. No rough running, missing, sluggishness or anything. Just WHAM and done! Can't wait to get it back. Should be done Thursday!

 

[NC-smokinlmm]

My 2012 took a dump on me, going 80 mph down the interstate in Wyoming, with 77,000 miles on it. (H&S Street Tune, FASS lift pump, cold air induction and 4" exhaust) A big shudder, dash flashed "Change Fuel Filter" then "Engine Power Reduced". Coasted to the exit ramp (fortunately it was MY exit!) that's when I realized the truck had completely shut down because I didn't have power steering anymore. Threw 7 codes, the first of which was Low fuel rail pressure. Most of the rest had to do with the truck having shut down and still moving faster than the CPU thought it should be moving. FASS filters had metal shavings in them. Factory filter had metal shavings in it. Still wouldn't start. Put it on a hook and took it to a diesel shop. Bottom line - they told me there is a service bulletin from GM on it. And the whole fuel system has to be replaced. (I have a copy of part of the bulletin where it mentions having to replace the whole fuel system if metal shavings are found.) So I'll have new everything, rails, injectors, pump, fuel lines, high pressure lines, etc. I asked the mechanic specifically and he said I have a CP3, not a CP4. That was a bit confusing because I'd been told by others that the 2012's all have CP4s. It's gonna cost me plenty to have it fixed. I didn't find out about the service bulletin until it was well into the tear-it-apart stages trying to find what all was damaged when the pump went out so don't know if I'll have a chance at getting anything back from GM for the repairs. Up until this happened, the truck was running like a champ. No rough running, missing, sluggishness or anything. Just WHAM and done! Can't wait to get it back. Should be done Thursday!

That's terrible luck man I hate to hear that. Unless you swapped out the cp4 the mechanic is wrong. I would not go back with a cp4, there are cp3 conversion kits available for relatively cheap.

 

[duratothemax]

106,000 miles on mine...has anyone done any studies regarding additive, if it helps at all?

I dont have time/money to dick with a CP3 conversion right now...maybe this coming spring. I could care less about performance, I just want it to be reliable.

 

[duratothemax]

My 2012 took a dump on me, going 80 mph down the interstate in Wyoming, with 77,000 miles on it. (H&S Street Tune, FASS lift pump, cold air induction and 4" exhaust) A big shudder, dash flashed "Change Fuel Filter" then "Engine Power Reduced". Coasted to the exit ramp (fortunately it was MY exit!) that's when I realized the truck had completely shut down because I didn't have power steering anymore. Threw 7 codes, the first of which was Low fuel rail pressure. Most of the rest had to do with the truck having shut down and still moving faster than the CPU thought it should be moving. FASS filters had metal shavings in them. Factory filter had metal shavings in it. Still wouldn't start. Put it on a hook and took it to a diesel shop. Bottom line - they told me there is a service bulletin from GM on it. And the whole fuel system has to be replaced. (I have a copy of part of the bulletin where it mentions having to replace the whole fuel system if metal shavings are found.) So I'll have new everything, rails, injectors, pump, fuel lines, high pressure lines, etc. I asked the mechanic specifically and he said I have a CP3, not a CP4. That was a bit confusing because I'd been told by others that the 2012's all have CP4s. It's gonna cost me plenty to have it fixed. I didn't find out about the service bulletin until it was well into the tear-it-apart stages trying to find what all was damaged when the pump went out so don't know if I'll have a chance at getting anything back from GM for the repairs. Up until this happened, the truck was running like a champ. No rough running, missing, sluggishness or anything. Just WHAM and done! Can't wait to get it back. Should be done Thursday!

Was it covered under warranty?

 

[duratothemax]

I replaced a friend of mines entire fuel system because of the cp4. It had a little over 100k on it and out of warranty. I tore the pump apart and saw the bores were all scarred up and one plunger wouldn't even move. The rollers on the bottom of t!he plungers had complete flat spots in them to where they wouldn't even ride on the cp4 cam right. Junk Pumps period!

How many miles out of warranty was it?

Does the cab have to come off to replace it?

 

[quadracer37]

How many miles out of warranty was it?

Does the cab have to come off to replace it?

don't need to lift cab. we do conversions weekly here in just 3-5 hours (on Already EGR deleted trucks) with EGR your talking closer to 10-12 hrs
all failures we've seen have been related to poor fuel quality/contamination. once they fail is what really gets expensive. 9 times of out 10 requires all new injectors, rail sensor, DRV Valve, Return line assembly with check valve, drop tank to clean, and clean all other fuel lines.

 

[duratothemax]

don't need to lift cab. we do conversions weekly here in just 3-5 hours (on Already EGR deleted trucks) with EGR your talking closer to 10-12 hrs
all failures we've seen have been related to poor fuel quality/contamination. once they fail is what really gets expensive. 9 times of out 10 requires all new injectors, rail sensor, DRV Valve, Return line assembly with check valve, drop tank to clean, and clean all other fuel lines.

Hmmmm...so I guess I should invest in an Airdog or Fass.

Like I said, I really do NOT care about performance on this truck. Its just for testing new products, and because all I want is to have a nice new(er), quiet, non-smelly, smooth, comfortable and RELIABLE daily driver...

 

[quadracer37]

Hmmmm...so I guess I should invest in an Airdog or Fass.

yes strongly recommended. additive never hurts either considering failures stem from lubricity & contamination 98% of the time.