what is the desired rail pressure? I hooked the quadzilla rail guage today and only got 10,000 with some throttle. before my truck died it was down in-between 130 and 0. Could my problem be my cp3? i know its not the relief valve.

 

22-26K. Sounds like you've got some big problems. How do you know your relief valve is working correctly? When you've got pressure dropping to almost zero it is typically the FPRV. It could also be your CP3 but I would certainly make sure the FPRV is working first.

 

dodge said they replaced it and the piece does look brand new. i also did some tests that floor-it-diesel had me do while on the phone.

 

Definitely sounds like the CP3 then. I would pull the return line and do the return line volume test just to make sure. I would hoping for a faulty valve then a CP3.

 

ohhh..me 2! how do you do the volume test?

 

Pull the return line going to the tank and stick it in a container that has graduated measurements on it. Start the truck and let it idle. You measure how much fuel you have after one minute and it will tell you if the FPRV is functioning properly. I'll have to look up the specs on the return volume thought. Cant remember off the top of my head.

 

There are a few things that happen in regards to rail pressure. The first is the supply to the CP3 which it looks like you have covered. The second is the command from the ECM to the FCA for rail pressure. The FCA then lets the CP3 make whatever pressure is commanded. What is commanded is compared with what the actual pressure is at the rail pressure sensor. If the two are withing paramters then your on your way. If not, the ECM will ikely shut the CP3 down via the FCA. The things that can make this haywire are the obvious, the CP3 has mechanically failed, injector(s) stuck open, FCA is bad, relief valve is bad or the ECM is bad.

 

i switched out the fca with another truck and it didnt fix it. the relief valve has been changed also. im hoping i can get another cp3.."under warranty" and that fixes the problem. the truck runs until it gets warm and then it shuts off and wont start for a few minutes. as the truck was warming, the quadzilla rail guage was dropping lower and lower until it hit 0 and then the truck died.

 

Any codes present?

 

only one about the ecm i believe. it doesnt have a check engine light on but that was the only code that was on the truck