I have a 04 5.9 that wont start without either, once started it will just idle perfect. Once you hit the throttle, it will not slow back down. The rail pressure will not come back down once raised. Any help appreciated.

 

Could the high pressure return be clogged?

 

Could it be a stuck FCA? Check your connection on the CP3 it might be loose. I'm pretty sure thats your problem. If your FCA is unplugged it will operate at full capacity causing high rail pressure. If its not loose I would look into getting it replaced.

 

I haved replaced the fca, then i changed the cp3, same problem, any more ideas?

 

I've got the same problem with a customers truck. Did you guys figure out what was causing the problem? I just agreed to work on the truck today.

 

APPS could be faulty. Check for codes!!

 

Thanks, I'll check.

 

Cycle the key three times. On the 3rd time leave the key on and they'll show up in the odometer.