LLY loses fuel rail pressure after it warms up

[hottlead]

Hey There, the problem started when I was pulling my trailer down the highway and noticed a lack of power and black smoke. When I got back home I used my CTS 2 insight to show me the desired and actual fuel rail pressures. When I first start it after a couple of days and drive it, the desired and actual pressures are the same and go up to 17k with normal driving. After about 3-5 minutes I notice the the actual pressure stops at 10-12K when it is calling for anything above that. It will drop more and max out at 8k or 6k and I have lost enough pressure more than once that it stalls out on me. If I wait a couple seconds it will start again, but will still max out at 8-10k usually. It is inconsistent in what psi it will max out at, but it is never higher than 11-12k after the first few minutes of driving and once it drops during a drive it never goes back up to normal pressure. I have an air dog lift pump on the truck and around 115,000 miles
Things I have done:
-Injector balance rate check. all within tolerance (2 are close to max deviation, but not failing)
-replaced all of the fuel filters (2 air dogs and a wix at the engine) and ran two bottles of diesel medic through it
-ran the return line off of the FPRV to a bottle to see if it was opening up due to a weak spring, but the bottle is dry.
I'm thinking now I have an issue with my, pressure regulator, cp3 pump or injectors. Does anyone have experience with symptoms like this? I have been reading other threads, couldn't find one with it having proper pressure when you first start it after sitting.
Thanks

 

[2004LB7]

Sounds like hot fuel returning on through the injectors issue. Have you checked the return on the injectors cold and warmed up?

 

[hottlead]

No I have not checked that. I will try to do that this weekend. I am not familiar with that issue though. Are you saying that the fuel temp is hot when it enters the injectors? If so what causes that issue?

 

[Bdsankey]

The fuel will heat up regardless, no way around it. It's a byproduct of being pressurized (adding work to the fuel) and then running through lines etc on top of the hot engine.

When the fuel system ages it's not uncommon to see injectors and or pump start returning too much fuel as it the fuel warms up/thins out. As said above I would recommend checking your injector and pump return volumes. These trucks, at their newest, are 18yrs old (2005) so it's not unreasonable to have fuel system components wear out.