CP4, HPP Failures - Root Cause Analysis

Scott Owner Moreno Valley, California Posted   Latest   Edited  
Question
Driveability
Drivetrain
2015 GMC Sierra 3500 HD 6.6L (8 LML) 6-spd (1000)
Cranks
Crank / No Start

Hello All,

I have quite a few customers with the 6.6L Duramax's and I've been seeing (for a while now) what is described in GM's TSB - 16-NA-102 which is a catastrophic fuel system failure. I just finished one of these up and it's quite an extensive & expensive job. As I'm working this I had other Duramax customers questioning what I was doing. Really, that much? Aw', crap.

This one, and another one I saw seemed like the failure started due to cavitation due to a leak on the supply side. This truck was towed in a few thousand miles ago for a no start and at that time (GM calls it a fuel filter shell now) the filter housing was leaking. I replaced that and a fuel filter and the truck primed and started.

Fast forward - it's towed back in and now the system is not developing the minimum of 1,885 PSI needed to start and run. Removing Fuel Pressure Regulator 1, a substantial amount of metal is seen and what is described in TSB 16-NA-102 is done. Another regular customer called and said his 6.6L LML truck was not starting. He had dragged his feet and took 2 weeks to get it towed in. With all the other work going on it would have been at least a week before I could get started on it. He said he really needed his truck back so he had it towed to the dealer who said they could get it done in a week. They already had 3 of these going on...

The $64,000 question - What is the cause of these failures and what can be done to prevent this, if anything?

My thoughts -

  1. GM has extended the filter change using the DIC, although tucked away and it requires some reading is "Change the fuel filter every 2 years, or if you've reached 22,500 miles. I have a customer that I haven't seen for a few years because he bought an LML in 2015. He wants a fuel filter replaced as the DIC said to change it 86,684 miles. How many filters have you put on? None, this is the first time it came up...Hmm.
  2. My understanding is GM has gotten away from Bosch and gone to Siemens for the L5P - 2017 on up. One change is they now have a lift pump. I have not heard any reports on the newer L5P engines, so I might take that as good news.
  3. I saw very few failures on the CP3 pumps, used on LB7's on up, and these problems started with the CP4 pumps. I've seen plenty of CP3 pumps that had leaks at the filter housing and they all lived. Is there a plating problem or just an inherent design flaw? I included a picture of where the metal comes from.

Thoughts?

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David Diagnostician
Independence, Louisiana
David Default
 

There are many factors that lead to CP4 failure. The number one problem is contaminated or "dry" fuel. These pumps need constant lube from the fuel to operate properly. This pump was actually used in the European market and was specced for their fuel. US fuel has a different SCAR rating than Euro blends. Our fuel has very little lubrication properties. The second cause is the laziness of GM. The

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Marlin Technician
Estacada, Oregon
Marlin Default
 

I certainly agree with your perspective of the supply system issues. Add in the fact that AC Delco sells a filter which more poor than the TP3018, and it is a problem that doesn't need to be. I can long been amazed at (what I see as) the foolishness of RAM and GM regarding their diesel fuel supply systems. The current RAM version uses a great dual filter system, by they did really stupid on the

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David Diagnostician
Independence, Louisiana
David Default
 

I use Airdog 4G. They are a clean install and the filtration is great. Fleece actually just came out with an in tank pump.

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Scott Owner
Moreno Valley, California
Scott Default
 

Thanks for the information. If I understand you correctly, you're recommending this to anyone that has a Duramax and a CP4 pump? I normally wouldn't recommend installing aftermarket parts, but in the case of this failure and the cost involved I'm thinking this would be a good recommendation for anyone with 6.6L and a CP4 pump. I've got a friend that was one of the guys that came by and I might

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David Diagnostician
Independence, Louisiana
David Default
 

Correct! The aftermarket diesel industry is one of the most innovative in the automotive aftermarket. Most of the guys grew up on farms and are self taught. I understand where you are coming from on the not recommending aftermarket parts. In this case, it's a great upgrade. The OE seems to short the consumer on research and development, but not on the initial purchase price.

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Marlin Technician
Estacada, Oregon
Marlin Default
 

Is there something about Airdog pumps which you think is superior to FASS? Have you found them to be reliable long term? Based on the input which I have received locally regarding Airdog quality is that is has been very poor, I also haven't found that their design to be superior to FASS. Thanks for the mention of Fleece; new name to me,

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Scott Owner
Moreno Valley, California
Scott Default
 

Thanks for throwing that out there Marlin. I guess I'll do some research on what would be best as there seems to be differing opinions on this.

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David Diagnostician
Independence, Louisiana
David Default
 

Airdog had problems in the past, the updated 4G motors are far better than previous generations. I have had very few motor failures on the new style.

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Scott Owner
Moreno Valley, California
Scott Default
 

Hi David, Thank you for the reply and your personal experiences! Thanks for the clarification that it wasn't Siemens, but Denso for L5P engine. I appreciate it!

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Taurayi Owner/Technician
Harare, Zimbabwe
Taurayi Default
   

I second what David Finch just said, I believe lubricity is the key to these pump failures, with USA ultra low sulfur diesel there is very low lubricity. So when you combine that with cavitation the disaster strikes.

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Michael Owner/Technician
Montague, New Jersey
Michael Default
 

As others have stated, lubricity is the issue. I tell my customers to use Stanadyne, Amsoil or Power Service additives. In the summer 2 oz for about 15 gallons. Winter wise they use it for anti gel and how much varies for how cold. I prefer Stanadyne overall.

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Labeed Technician
Baghdad, Iraq
Labeed Default
 

hello Scott What do you think of an adjustment to this pump? I mean to overcome the consumption problem because of diesel type Consumption due to lack of oil in diesel type This is due to friction and its consumption quickly .

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Scott Owner
Moreno Valley, California
Scott Default
 

Hi Labeed, If I'm following you here, you're talking about an additive to make up for the lack of lubricity in today's diesel fuels? That might be a good idea! Thank you,

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Josh Technician
Lynchburg, Virginia
Josh Default
 

You had mentioned about the changing of filters, at our shop we try for every 10,000. I put a sticker on the windshield just like an oil change sticker, seems to help some folks remember to do it even if they don’t come back to us. We also have a landscape company with a 5500 and the gentman that runs that company changes his oil and fuel filters every 5000 or so. Over maintain is cheaper than

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