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Hi, I’m curious with all the CP4 failures how many of you have had this happen while religiously using some fuel treatment? Vs using? May happen anyway or prolonging the Inevitable.
I’ve used Schaeffer from day one in my 14 lml and I’m currently at 25,000. Thanks
 

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Is the CP4 problem because they used a pump incompatible with ULSD due to it's lack of lubricity? Or am I thinking of something else?
 

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This will start a big debate. I've done a lot of research and have almost 300k miles of LML experience as well as LML friends too so here's my opinion.

General concensus seems to be that the CP4 was designed for the European market where they have better fuel and apparently has not been as big an issue over there as it is here with GM.

The CP4 is not as reliable or durable a pump as the CP3 that was used up through 2010. Ford has used the CP4 as well with a little better results but they also used it in tandem with a lift pump.

Many guys get many trouble free miles from the CP4, however, many have had premature failures. I put a FASS pump on mine when I bought it at 98k miles. I know several guys that run either a FASS or Airdog with good results. Some guys will say these pumps may actually do more harm than good and actually just promote a simple lift pump. I got 244k miles out of mine without failure but when I had to perform some heavy maintenance on mine last summer, I replaced the pump, injectors and rails at the same time.

My most up to date theory is that CP4 life corresponds to the fuel you're feeding it. Where I live in the Midwest like most of the rest of the nation now, about all you find at the pump is B5-B20 biodiesel, which is arguably about the best thing you can do for your fuel system. Bio blends at only about 2% provide more lubricity for your fuel system than any additive you can dump in your tank. So the guys that are still running bone stock without additives and achieved many trouble free miles are probably running almost solely on bio fuel.

I wouldn't fuel anywhere that I was afraid of fuel quality or contaminants, especially water. Most sediment type contaminants can be removed by filtration but whether or not you're getting most of the water out of your fuel could be another story. It seems to be a little tricky to trap all of it. Many guys, myself included, report rarely ever finding much if any water when we open the drains. Some additives try to take it on through the system while some try to take water out the drain, emulsifiers vs demulsifiers.

Bottom line, if you ensure a good steady supply of clean fuel to your pump, without contaminants, you probably have a good shot of having a happy CP4 pump for many miles. If you elect to remain stock, I'd spring for the best fuel filter you can find, probably AC Delco, change it religiously and always try to buy top quality fuel from a high volume source. But if you want to hedge your bets, positive pressure to the CP4, added filtration and fuel additives all seem to be good investments.

Schaefers has good stuff but if you want to see how many of the top fuel additives stack up against each other, refer to the Arlen Spicer diesel fuel lubricity additives study results. It's several years old now but still good reference. The only bogey now is if one or more of the additive companies has changed formulation. You would hope if they have that the change was an improvement.

That's just my opinion. I could be wrong:)
 

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General concensus seems to be that the CP4 was designed for the European market where they have better fuel and apparently has not been as big an issue over there as it is here with GM.
That was pretty much my understanding



I wouldn't fuel anywhere that I was afraid of fuel quality or contaminants, especially water. Most sediment type contaminants can be removed by filtration but whether or not you're getting most of the water out of your fuel could be another story. It seems to be a little tricky to trap all of it. Many guys, myself included, report rarely ever finding much if any water when we open the drains. Some additives try to take it on through the system while some try to take water out the drain, emulsifiers vs demulsifiers.

Bottom line, if you ensure a good steady supply of clean fuel to your pump, without contaminants, you probably have a good shot of having a happy CP4 pump for many miles. If you elect to remain stock, I'd spring for the best fuel filter you can find, probably AC Delco, change it religiously and always try to buy top quality fuel from a high volume source. But if you want to hedge your bets, positive pressure to the CP4, added filtration and fuel additives all seem to be good investments.
I'm fortunate to have a high volume Gate gas station 2.5 miles from the house and has been where I get 90% of my fuel. If I go anywhere else I avoid backwoods and ghetto gas stations. If I have no choice because I'm running on fumes, I'll get just enough to get me home and I'll fill up at my home station. I guess that's why I'm still on the original injectors and pump after 11 years and 235k miles.
 

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Discussion Starter #5
Thanks for your reply. How would you know if your fuel is good quality without having it somehow tested? Does diesel vary that much between suppliers and who adds the sulfur?
 

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who adds the sulfur?
Sulfur naturally occurs in the crude petroleum that is refined into fuel. In the past, there was a looser specification on the amount that could be present in the final product. Refiners have been forced by regulation to add cleanup stages on their processes to remove most of the sulfur that remains in the final product, hence the Ultra Low Sulfur designation on modern fuel.
 

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Thanks for your reply. How would you know if your fuel is good quality without having it somehow tested? Does diesel vary that much between suppliers and who adds the sulfur?
There probably isn't any more difference in quality of fresh diesel than gasoline. The problem is that gas and diesel go bad over time so if a gas station doesn't move much fuel, it goes stale. Making that much worse is that diesel is hydroscopic. That's why diesels have water separators and gassers don't. So, when diesel sits in a tank too long it get's water in it and algae can grow in it. The algae will just clog the filter but water wrecks your fuel pump because there's no lubricity which the pump requires. As the pump eats itself, bits of metal get into the injectors and wrecks those. $$$$$$$$$$

Always try to get fuel at busy stations that turn over a lot of diesel.
 

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There's probably something to be said about underground vs above ground tanks as well. There are still some stations using underground tanks. We have a local station that fights water in their fuel due to underground tanks, especially when we get a lot of rain in a short period of time. Any time you see above ground tanks, that's a good thing.
 

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still some stations using underground
Where are they not?
Major EPA changes years ago dealing with storage, put a good chunk of small spots out of biz....too costly to upgrade the tanks. Above ground storage requires a large retention design surrounding the tank(s)....even the large tank farms along the Houston ship channel, same thing.

get a lot of rain in a short period
That sounds like more of a site issue with drainage, vs the tank inlets.
 

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No sure if it helps or if it Just makes me feel better inside. I only fuel up from my slip tank in my truck or my high stand tank at home. Both tanks I have a 2 filter water separator on so all my fuel gets from the station pump to my slip tank then goes either in my truck or goes in my big tank at home and I change my water block filters every 3 months. So like I say not sure if it helps but it makes me feel good inside going through the water block filters more before goes in my truck tank.
 

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No sure if it helps or if it Just makes me feel better inside. I only fuel up from my slip tank in my truck or my high stand tank at home. Both tanks I have a 2 filter water separator on so all my fuel gets from the station pump to my slip tank then goes either in my truck or goes in my big tank at home and I change my water block filters every 3 months. So like I say not sure if it helps but it makes me feel good inside going through the water block filters more before goes in my truck tank.
I'm sure it helps. I'm at 240k miles on the original pump and injectors, I think because I'm very careful where I get fuel. One day when I have some land, I want 2) 1000 gal diesel tanks with a polisher and buy fuel in bulk. I still remember the fuel shortage from '08 or '09. I should be there already but life...
 

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I'm on my second LML and have not had a cp4 fail - yet. My dealer, who I trust, says it is water that kills them. I use additive and plan to have a cp3 conversion done just before my truck goes out of warranty.
 
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