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I have a 2016 Sierra LML with 76K miles, wouldn't fire, towed to the dealer. CP4 blew up, dealer is replacing fuel system, pump, injectors, lines, dropping tank and cleaning, etc Warranty :x, 12k estimate for repairs if it wasn't warranty:surprise:

My question has GM upgraded the CP4 replacement pump? I understand the suspected cause is lack of lubrication from North American fuel, since I'm not likely to move to Europe, what's the best way to prevent another failure?

Thanks

Bill
 

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......My question - has GM upgraded the CP4 replacement pump? I understand the suspected cause is lack of lubrication from North American fuel, since I'm not likely to move to Europe, what's the best way to prevent another failure? Thanks Bill
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wow - glad you are having this done under warranty. Unfortunately, as a warranty repair GM "calls the shots" so even if you bought your own a CP3 to do the conversion, the dealer couldn't install that...he HAS to use a GM spec. part. Another CP4.

You may have seen the extensive posts about resolving the CP4 issue by buying and installing the CP3. I did that for peace-of-mind.

Bear in mind there are tens of thousands, if not hundreds of thousands of CP4 equipped Duramaxes going hundreds of thousands of miles on their CP4's with no issues.

Yes, I gambled some four grand to avoid the remote risk of having to spend ten grand. As I noted in other posts, given the kind of use I bought my Duramax for, it was an appropriate gamble. Depending on how you use your Durmax...it might well be worth it to stick with the CP4.
 

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WOW mine is a 2016 with 67k miles on it. Now I am concerned more than ever.

Currently waiting on a shop to get me the correct exhaust pipe as I was in the process of having a delete done. First trip there they were sent the wrong pipe, ended up being for a F-250 instead of my Duramax. Maybe that was fate intervening on my part. Second guessing that delete now with 1 year of warranty left on the truck.

This CP4 issue is BS. I swear if this happens to my truck I am jumping on the class action lawsuit against GM on this. No way anyone should be stuck with a $10-12k repair bill on a modern truck built these days.
 

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I have a 2016 Sierra LML with 76K miles, wouldn't fire, towed to the dealer. CP4 blew up, dealer is replacing fuel system, pump, injectors, lines, dropping tank and cleaning, etc Warranty :x, 12k estimate for repairs if it wasn't warranty:surprise:

My question has GM upgraded the CP4 replacement pump? I understand the suspected cause is lack of lubrication from North American fuel, since I'm not likely to move to Europe, what's the best way to prevent another failure?

Thanks

Bill
People have said there is a new version of the pump but no one has actually been able to show somewhere that definitively states there was any actual changes to it. the CP4.2 is NOT a new revision of the pump despite what some say.

best prevention is added filtration (see bobs fuel filter thread for recommended filters) and lubrication. For the lubrication, you have 3 options, run bio diesel / bio diesel blend, or run a good additive like optilube, there are some additives that have been shown to NEGATIVELY impact lubricity though so dont just buy anything at the store. the last option is to use bio diesel and additives. There is also a "fuel system saver" which is a fine mesh screen that is supposed to prevent a failing CP4 from trashing the whole fuel system, though there have been no reports of a truck with one in stalled having a failure so its an unknown.
 

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WOW mine is a 2016 with 67k miles on it. Now I am concerned more than ever.
relax,,I'm at 95k on mine and I beat on this puppy.will be filling it w/ freashly cut maple tree tomorrow.
get diesel at high volume stations and maybe run some bio 5-10% in it once and a while.
 

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I'd be curious to know a few things:

1. Have you owned the truck since new?
2. Have your ever ran any fuel additives? Which?
3. Do you typically run any bio diesel? Pumps are usually labeled.
4. Where do you buy your fuel?
5. Have you ever had a known incident of water in fuel?

If it were me, I'd question the hell out of the dealer doing the repair. That is of course unless you know them and are comfortable with them. I've heard horror stories about dealers that weren't very familiar with the Duramax that installed a new fuel system that didn't last very long. Good luck!
 

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I’m relaxed contrary to my post. I’m really picky where I buy fuel. My truck is babied. I never push it, I’m old. No need in all that stuff. I only drive it to work 5 days a week total 130 miles. It lives in a nice big garage. I buy bio at times but not all the time. Mostly Exxon Mobil or marathon locally. Change my fuel filter once a year regardless. This thing blows and reaffirms what I said earlier I’d have to seek legal attention because this truck is not abused or used to the extent I’d have to fork out 10-12k to repair it. It’s paid for to. I love the truck but I do not like reading about this CP4 issue which I knew about before buying it. I do still tow s you hauler with it annually maybe twice a year. Most my toes are light duty with a 6x10 trailer and two motorcycles which ain’t no weight or stress on this truck.
 

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I’m relaxed contrary to my post. I’m really picky where I buy fuel. My truck is babied. I never push it, I’m old. No need in all that stuff. I only drive it to work 5 days a week total 130 miles. It lives in a nice big garage. I buy bio at times but not all the time. Mostly Exxon Mobil or marathon locally. Change my fuel filter once a year regardless. This thing blows and reaffirms what I said earlier I’d have to seek legal attention because this truck is not abused or used to the extent I’d have to fork out 10-12k to repair it. It’s paid for to. I love the truck but I do not like reading about this CP4 issue which I knew about before buying it. I do still tow s you hauler with it annually maybe twice a year. Most my toes are light duty with a 6x10 trailer and two motorcycles which ain’t no weight or stress on this truck.
For a little peace of mind you could pull your inlet metering valve out and inspect it for debris. If it's clean, you're good.
 

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It is a bummer when they let go for sure. I feel fortunate my business' 2011 3500Dually is still running strong on original at 190K. I am also fortunate I have B20 biofuel a mile from my business. I'd say 80% of the fill ups have been bio. I did throw a Kennedy dual lift pump and filter/separator on about 70K miles ago to try and help a bit.
 

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Unfortunately, I had a similar experience. About a week after buying my LML with around 120,000 miles on it, my CP4 decided it was time explode and my repairs were not under warranty. I too debated whether I should just replace the CP4 or spend the extra $3,000 or so for the CP3 conversion. Ultimately, I ended up doing the CP3 conversion because I didn't want the possibility of a failed CP4 in the back of my mind throughout the ownership of my truck. In all honesty, it probably won't happen to you again, but the cost of the CP3 would probably put your mind at ease a little more and I would say it's probably worth swapping eventually.
 

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failed CP4 in the back of my mind throughout the ownership of my truck... probably won't happen to you again, but the cost of the CP3 would probably put your mind at ease a little more and I would say it's probably worth swapping eventually.
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couldn't agree more - that's why I did that to mine !
 

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I confess that I'm into data driven decisions, so I'd like to have some feedback on the CP4 vs CP3 questions.

Does anyone have any actual statistics on the failure rate of CP4s in trucks that are kept completely stock?

If poor lubricity in US ultra low sulfur fuel is the CP4 Achilles heel, exactly what is it about the 50 state compliant CP3 conversion kit that makes it a better option vs the CP4?

Is there any data available on the effectiveness of the FPR upgraded LMLs, using the Wherli FPR, for example, with respect to how well the downstream fuel system was protected from a failed CP4?

Thanks in advance for your responses!
 

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-- and what filtration was used ahead of the failed pumps?
-- and was it tuned to overfuel, increasing the chances of cavitation?
---- "it's only ever run the xyz power setting and it's never pushed hard and ..."
-- and was it a top tier fuel being used?
-- and were any additives used? (in the often quoted study, some were shown to make scar rating worse)
---- if used, was it at label rate? (some seem to think if a little is recommended that a lot must be better....)
-- etc etc


Far far too many variables and unknowns to have any good idea about true failure rates for 'completely stock' units.
 

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I have read that as much as 7% of CP4 fail on LML Duramax. I have LML with 113K, runs great. I use Stanadyne fuel treatment every fill (since 80k when bought), and always fill at "busy" outlets. If I have to replace something in future involving tear down (injectors), I will replace with CP3. Everything on my LML is stock. My state (WA State) just busted several diesel garages for removing pollution equipment, fines up to $160K. 3 emails asking about cost of replacing CP4 were not answered.....at all.
 
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