Originally Posted by the man in black
So if its primarily water, why did the separator filter it out?
The separator can be inadequate in two cases: you pump a load of very bad diesel into your tank, unknowingly, that has a lot of water in it. It overwhelms the separator. The other case is that the separator is working, and over time fills up the bottom water storage capacity. The user never drains it, and it triggers a WIF light. By the time the user gets done driving, water has passed through the separator up to the high pressure pump. Only a tiny amount of water can cause rust which starts the failure process.
Not sure if you had the joy of experiencing a failed CP4, but I did and I had my fuel tested...twice. CLEAN. I joined the lawsuit in California against GM and for some lawyers out of Texas...holy . I thought i researched the topic, nope. These guys knew everything...they knew it was not from water in my fuel before I told them. It is LACK OF LUBRICATION in diesel #2. Air in the pump plays and good part too though if presented.
Lack of lubrication is correct, but the reason isn't a design flaw in the pump. It is lack of lube due to water or some other foreign substance such as DEF or gasoline. Water strips the small amount of lube diesel fuel offers. It also creates rust when the pump isn't running, which then strips off and into the system when it restarts.
Originally Posted by dieselenthusiast
He seemed very confident in his knowledge. I don't know where he got his information, but his information was stated as fact and not opinion. He specifically said the lift pump in the Cummins doesn't pose the problems that Ford and GM had with their systems, which is why Ford and GM are being sued. Bosch has said and continues to say that their pumps are suitable for U.S. fuel.
The fact that we are not seeing failed CP4 pumps with the Cummins does give some support to the theory that Ram has better fuel delivery to the CP4. If the problem was fuel, then we should see just as many failures in the Cummins than we do with GM and Ford.
There is a reason why FCA/Cummins added the CP4 to their trucks. They would not have done so if they expected the same failure rate as GM and Ford. And there is a reason why GM and Ford discontinued the CP4.
Ford has not discontinued the CP4. Not whatsoever. GM discontinued in 2016. If it was so problematic for Ford after six years, they would have also switched suppliers. But they haven't, which means it isn't really a problem. Cummins chose to use the CP4 because it does everything for them that they need, and they likely have a good relationship with Bosch over the years supplying CP3 pumps, fuel injectors, control units, etc. It has zero to do with fuel supply. You can state something as fact all day but it doesn't make it true. If what he said was correct, how could ANY LML Duramax still be surviving today? None of them had a lift pump. And yet there are some with huge miles still operating perfectly today. In fact, there is a video on youtube of one for sale at a dealer...1,071,000 miles on the LML engine, no rebuilds, nothing major. Running fine. The original owner used it to hot shot RVs from manufacturer to dealers all over the country.
It's hard to imagine intelligent people really believing a company like Cummins can figure out how to make a CP4 never have a problem, while companies like GM and Ford never could after years with the same product.
And this thing with US vs Euro fuels...is completely ridiculous. Bosch entered into contracts with Ford and GM and others to supply the CP4 pump. If it really wasn't suitable for US diesel, Bosch would have informed them and Ford / GM / Others would have been well aware. Nobody wants ruined reputations, millions in warranty claims, and lawsuits. Furthermore, the CP4 is not quite an "off the shelf" pump supplied to different manufacturers. The CP4 on a Ford is customized for the Powerstroke 6.7. Ford and Bosch worked together on the final specs, no different than Bosch worked with GM and others. These units were tested, torn apart, re-spec'd, and retested. It isn't rocket science. Obviously, the pumps are not interchangeable. Ford is advertising 36k PSI from it's CP4 pump on the 2020 Powerstroke. RAM advertises 29k from its CP4 pump on the 2019 Cummins. Clearly tuned and customized differently.