Talking someone at GM that has a brain and authority - Page 2 - Chevy and GMC Duramax Diesel Forum
11-16 LML Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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post #11 of 30 (permalink) Old 07-31-2019, 01:37 PM Thread Starter
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Originally Posted by Gatordog View Post
The dealer can contact Corporate for you and start a review, if under warranty. The problem is, finding a good dealer. The CP4 is a known issue, so GM canít act dumb. The Ford 6.7 uses the same IP, but since they have a lift pump the failures are not as common, and they can modify the CP4 so when it fails it doesnít take out the injectors. Donít know if that same modification will work on the LMLís. You can go with the Cp3 conversion, or stay with the Cp4 and add a lift pump. The CP3 would be better. Regardless youíre looking at over 10k to fix
Truck is not under warranty. Its a 2012 with 75830 miles. I bought it new. I'M aware of the cp4 issues I am not new to the forum. Has been at dealer since 07/13/19 They say GM want help I just want to talk to someone that has 1/2 a brain and someone off shore. My dealer says they have not had to replace any of the cp4 replacement pumps in 6 or 7 years they claim its a revised pump.

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post #12 of 30 (permalink) Old 07-31-2019, 01:41 PM Thread Starter
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Originally Posted by monkeyman View Post
CP4 is prone to going bad from lack of lube try 888-988-7267
This is the number i have called you get connected to a customer service person over seas im trying to find a direct number to talk to corp her in the usa.

2012 GMC Sierra 2500HD Diesel 2wd Crew Cab. Stock. 200 mile regen club
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post #13 of 30 (permalink) Old 07-31-2019, 02:44 PM
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Originally Posted by Gatordog View Post
The dealer can contact Corporate for you and start a review, if under warranty. The problem is, finding a good dealer. The CP4 is a known issue, so GM can’t act dumb. The Ford 6.7 uses the same IP, but since they have a lift pump the failures are not as common, and they can modify the CP4 so when it fails it doesn’t take out the injectors. Don’t know if that same modification will work on the LML’s. You can go with the Cp3 conversion, or stay with the Cp4 and add a lift pump. The CP3 would be better. Regardless you’re looking at over 10k to fix
Truck is not under warranty. Its a 2012 with 75830 miles. I bought it new. I'M aware of the cp4 issues I am not new to the forum. Has been at dealer since 07/13/19 They say GM want help I just want to talk to someone that has 1/2 a brain and someone off shore. My dealer says they have not had to replace any of the cp4 replacement pumps in 6 or 7 years they claim its a revised pump.
I would not go back with a CP4, you never know when those are going to fail, one bad tank of diesel and you are replacing it again. The dealer is going to install a CP4, unless you supply the CP3. Problem with that is they will not warranty the CP3.
The revised one fails just as bad.
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post #14 of 30 (permalink) Old 07-31-2019, 04:17 PM
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Originally Posted by Gatordog View Post
The revised one fails just as bad.
where did you see that?

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post #15 of 30 (permalink) Old 07-31-2019, 04:33 PM
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Originally Posted by Gatordog View Post
The revised one fails just as bad.
where did you see that?
The CP4.2 is still the same bad design, has higher output. These Cp4 ‘s fail on all vehicles that use them (ford, VW, GM) But the failure rate is much higher on the GM, because they don’t have a lift pump. The lift pump adds extra fuel that’s used to lube and cool the pump. So they will fail on the others, but not as bad as compared to the lml.
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post #16 of 30 (permalink) Old 07-31-2019, 04:43 PM
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Originally Posted by 6686L View Post
==========================================
A "lift pump" is the answer to the CP4 failure problem? Anybody have any statistics on that ? Anyone know of a CP4 "gernading" on a Duramax equipped with a lift pump?
Yes trucks with lift pumps have grenaded a CP4, see the CP4 failure thread.

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post #17 of 30 (permalink) Old 07-31-2019, 05:21 PM Thread Starter
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Well it's getting a cp4 it has been at the dealer since 7/13/19 that's the day it failed it was a saturday morning I had to do something then it is a company truck for my landscaping company the dealer started working on it yesterday they say it always takes them 2 weeks to get all the parts In they have been nice enough to loan me a new truck and said I can pull a trailer with it first time I have ever had a dealer loan a truck and say it's ok to tow a trailer with it I will just have to cross my fingers and pray this one stays together

2012 GMC Sierra 2500HD Diesel 2wd Crew Cab. Stock. 200 mile regen club
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post #18 of 30 (permalink) Old 07-31-2019, 06:25 PM
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Originally Posted by Gatordog View Post
The CP4.2 is still the same bad design, has higher output. These Cp4 Ďs fail on all vehicles that use them (ford, VW, GM) But the failure rate is much higher on the GM, because they donít have a lift pump. The lift pump adds extra fuel thatís used to lube and cool the pump. So they will fail on the others, but not as bad as compared to the lml.
Lift pump has nothing to do with lubing, & cooling the CP4, just takes some of the strain off the CP4 doing all the work. Lift pump doesn't add lube with extra fuel, it' the fuel itself that needs the lube, that's why you should use an additive. CP4's have failed even with a lift pump, tons of threads on it, do some reading.

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post #19 of 30 (permalink) Old 08-05-2019, 05:57 AM
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Everybody says add a lift pump to help your CP4 and I agree, I've had good results. I bought a 2012 with 98k miles and immediately added a FASS150 and got 244k trouble free miles out of my fuel system. It's nearly always mentioned that the lift pump pushing fuel to the engine takes strain off of the CP4 and I'm sure that's true. The part that is rarely mentioned is that the added filtration and particularly the water separator filter, will help send cleaner, more pure fuel to the engine.

I think something that gets missed a lot is the fuel that we buy, too. I buy almost nothing but minimum B5 bio fuel locally, which is known to be better than any fuel additives when it comes to lubricity, which is likely what determines the life of your CP pump. I wish there were some data on bio fuel versus non-bio fuel when it comes to life of a CP4 pump. Maybe it's out there but I haven't seen it.

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post #20 of 30 (permalink) Old 09-11-2019, 09:45 AM
 
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Anyone know if there is a technical service bulletin out for it? Mine blew yesterday and I am 15k miles over warranty, but still within the 5 years. Sometimes they extend for specific TSB issues, but I'm sure my luck is on the wrong side of this one.
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