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Discussion Starter #21 (Edited)
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.
There is no service bulliten or anything out for the cp4 pump good luck getting any help from GM with the repair I didn't so you have a 115k on your truck you can call GMC customer service and they will put your info into a formula to see if you will get any help I was declined because my truck was 764 days out of warranty but it only had 75830 miles on it. Make sure your dealer checks the fuel if it's due to bad fuel your insurance company may help my repair it 10k to fix dealer gave me a 3 year unlimited mileage warranty good luck to you
 

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Any correspondence I've ever had with GM customer support has been useless not very happy with them at all but good luck to you regardless
 

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Yes trucks with lift pumps have grenaded a CP4, see the CP4 failure thread.
I'm under the impression that the "lift pump" that helps prevent CP4 grenading refers to a lift pump with the combined water and fuel filters. As I understand it, the problem is the result of water and/or particle contamination and/or air being pulled into the CP4. I'm pretty sure a lift pump with filters will help make a poorly designed pump last longer, but if I were faced with replacing one, I would opt for a CP3 conversion just for the peace of mind. Another reason to hang on to my antique LLY.....
 

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Discussion Starter #24
Any correspondence I've ever had with GM customer support has been useless not very happy with them at all but good luck to you regardless
I agree with they are totally helpless refuse to connect you with anyone that has a say so or any authority I got 0 help and joined a class action law suit
 

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Discussion Starter #25
Yes trucks with lift pumps have grenaded a CP4, see the CP4 failure thread.
I'm under the impression that the "lift pump" that helps prevent CP4 grenading refers to a lift pump with the combined water and fuel filters. As I understand it, the problem is the result of water and/or particle contamination and/or air being pulled into the CP4. I'm pretty sure a lift pump with filters will help make a poorly designed pump last longer, but if I were faced with replacing one, I would opt for a CP3 conversion just for the peace of mind. Another reason to hang on to my antique LLY.....
Dealer checked my fuel no water or any other contaminants found in my fuel I have also seen them fail with a good lift pump
 

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I'm under the impression that the "lift pump" that helps prevent CP4 grenading refers to a lift pump with the combined water and fuel filters. As I understand it, the problem is the result of water and/or particle contamination and/or air being pulled into the CP4. I'm pretty sure a lift pump with filters will help make a poorly designed pump last longer, but if I were faced with replacing one, I would opt for a CP3 conversion just for the peace of mind. Another reason to hang on to my antique LLY.....
The ACDelco/Racor filter used on LML is an excellent' water filter.
 

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Discussion Starter #29 (Edited)
............ I have also seen them fail with a good lift pump
Can you provide a reference?
There is a thread on here cp 4 pump failure you can search for it people there had failures with lift pumps one of the main problems our us diesel does not meet the scar rating that basch spec for the pump
 

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