Truck is a 2014 F450 with roughly 200,000 miles on it. Full delete with Tyrant tunes, I've had it for about 60,000 miles and a couple of years with this configuration, nothing has changed recently.

I've been having a problem recently with my truck losing power under load. When it first happened, I changed the fuel filter and the problems seemed to clear up for a little while but then returned. I changed the filter again thinking maybe I'd just gotten some dirty fuel but, this time it hasn't really cleared up. I also had a P0228F code that was intermittent on and off for some time but never affected drivability, I went ahead and replaced the Fuel Pressure Control Valve on the fuel rail and it has cleared up the code and improved my problem some but, not eliminated it completely. Here's where I'm at now.

If I'm parked, I can rev the motor up sometimes to almost 4,000 RPM, other times it won't go past about 3,200. I've watched the fuel rail pressure in Forscan when doing this and it's either at or above the command value.

If I drive it, it does pretty well up to about a 70% load and then it'll drop off. Watching the fuel rail pressure, what I see is that it tracks the command value up to about this point and then the pressure drops off from 20k PSI to somewhere around 4,000 - 8,000 PSI, the truck just sort of plateaus and I have no more power. If I back off the accelerator and let it shift into the next gear, it'll have good power again up to about that point and the same thing repeats. I don't think it's junk or a restriction in the line because it will flow good fuel volume at high pressure, it just seems to drop off when the load gets high for some reason.

Below is a screenshot from a Forscan log showing what it looks like right before it drops off. For some reason, I wasn't able to get the power drop logged, I'm not really sure what I'm doing wrong with saving the log.

If anyone has any suggestions, I'd love to hear them. I'm at a loss at this point.

 

Make sure the main fuel filter canister is tight. You may be sucking just enough air to cause the truck to lose power. Just a guess

 

That was actually a problem early on, when I replaced the filter the 2nd time I didn't get the one on the rail tightened fully and it was stalling out. We fixed that but, I'll check it again as it wasn't me that did it so it could still be a bit loose.

 

Hopefully it's not a air in the fuel problem as that wouldn't be good for the HPFP.

 

Here's a datalog that shows the way the pressure falls off. The 7th line down is the fuel volume and when the pressure falls, it's showing that it's pushing 1.97 - 2.0 L/h. The only PID I see that looks like low pressure fuel is Low Pressure Fuel System Switch, which has a constant value of "Not Low." It's still not throwing any codes.

I took the fuel filter housing off and replaced the o-ring just because, it was tight already but I figured it was worth trying.

 

I took the truck into the shop Monday, they called and said it looks like the CP4 is worn out. It's failing a HPFP test and consistently dropping off when the command pressure goes above 27,000 PSI. I consider myself lucky to have gotten 195,000 miles off the original pump and that it wore out instead of detonating and sending metal into the fuel system. Since I'm going to have to replace it though, is there anything better available now? I know there's a CP3 change available for the Duramax but, I haven't seen anything for the Powerstrokes yet. If there's something I can do to strengthen this weak point in the truck when we replace the pump, I'd like to go ahead and do it now since I'm going to be paying for the labor anyway.

 

I'd say you're very lucky it didn't grenade and take out the injectors. Are they going to pull and check the injectors for proper function?


It depends on how you use and drive the truck along with how long you intend to keep that truck. If you run it in the tow tune, a stock CP4.2 would do it. I'd get a hold of these guys because they are the sheyet when it comes to our Bosch HPFPs. Here's an example of one their pumps with one of their metering valves installed with the stock fuel output. They also have more performance CP4.2s also.

https://spediesel.com/products/exergy-improved-cp42

SPE Diesel is located in PA and they do 6.7 Powerstrokes. Another place to get a hold to talk to someone to find out what exactly you need.

Also, if you are going this far, get yourself a air removing system like AFE's DFS780. It will remove the entrained air and make the pump and injectors last longer. But you did pretty good it seems without it. Just an idea.
This the system I want for my truck. There's also FASS and AirDog. FASS has the most complicated installation, the AiRDog is easier but the AFE is plug and play. Just throwing this stuff out there.