CP 4 Pump Failure - 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 #1 of 220 (permalink) Old 12-19-2013, 01:21 PM Thread Starter
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CP 4 Pump Failure

I am hearing people talk about the concern with potential CP 4 pump failures. But I have not heard from anyone who can speak 1st hand as far as the actual nature of the failure

Specifically... What part(s) are actually failing And has anyone examined the failed part closely to identify cause of the failure.

Is there premature wear being found or are the parts not holding up under the demands of the pump within its required operating parameters.

I would like to know if there is (for example) any indication of any seals, rings, bearing, etc that are failing first and that being the cause of a much bigger failure.

Curious if anyone has that kind of information or can possibly show us a unit that has failed.

Thanks.


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post #2 of 220 (permalink) Old 12-19-2013, 01:40 PM
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I saw a CP4.2 off a 6.7 Scorpion that had a piston pile up on the cylinder wall. Broke the input shaft and grenaded the pump. Cracked the housing actually. I'll look for pics.
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post #3 of 220 (permalink) Old 12-19-2013, 01:42 PM
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From what I've read, it happens so fast that it would be hard to tell what failed first, because they grenade.

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post #4 of 220 (permalink) Old 12-19-2013, 02:01 PM
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I've heard of piston rollers getting galled up, binding up on the cam and voila! "Multi-piece fuel pump"!
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post #5 of 220 (permalink) Old 12-19-2013, 02:19 PM
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If you tally up the amount of reported CP4.2 failures and compare it to the number of pumps that are still functioning in LMLs, the outlook isn't quite so grim.
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post #6 of 220 (permalink) Old 12-19-2013, 02:26 PM Thread Starter
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Joker... What causes the piston to do that? (Gall). Do these pumps see much heat? Is it from lack of fuel to the pump or possibly cavitation resulting in air getting into input side of pump?

Is this happening on stock trucks, tuned trucks, etc?

Is the kind of fuel we run today really a contributing factor? Not sure if I can completely buy into that theory?

If it a piston problem I can see how that can be catastrophic. But if it is a piston problem I also believe it is an relatively easy fix for GM to have Bosch upgrade newer units.

I am struggling with a unit being out there for 4 years or better and no one know any more now than 4 years ago.





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post #7 of 220 (permalink) Old 12-19-2013, 02:34 PM
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Quote:
Originally Posted by MarkLML View Post
Joker... Does it agall up as a result of


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1. Sh*t fuel (back to scar ratings and general fuel quality)
2. Lack of lubrication (water in fuel is bad for pumps lubricated by diesel fuel AND/OR running the pump dry)
3. Straight-up faulty parts and or assembly (it happens)

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post #8 of 220 (permalink) Old 12-19-2013, 02:43 PM
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Bosch clearly states that their CP4.2 pump requires 460 micron scar fuel or better. The lower the scar rating, the higher the lubricity.

The US standard for diesel fuel is 520 scar.

The Canadian standard for diesel fuel is 460 scar. It's no mystery why there have been fewer reported failures in, Canadaland.

Last edited by JOKER; 12-19-2013 at 02:48 PM.
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post #9 of 220 (permalink) Old 12-19-2013, 02:44 PM
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Bosch also published, many times, that pumps exposed to 500 scar fuel are expected to last 1000 hours.
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post #10 of 220 (permalink) Old 12-19-2013, 02:46 PM
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Quote:
Originally Posted by JOKER View Post
If you tally up the amount of reported CP4.2 failures and compare it to the number of pumps that are still functioning in LMLs, the outlook isn't quite so grim.
Agree on the current overall failure rate 'today' but nobody can say what they'll be after some time in the field. Combine that with the hefty price tag that could strike anyone at any given moment and you can see why some of us are rightfully concerned and asking questions.

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