Hey all,
I have a 2006 3500 HD. I bought it ~2 years ago and shortly after the engine blew. Took it apart and just recently had it rebuilt. It's been about 800 miles since the rebuild (~245K total miles) and I've noticed that the fuel rail pressure 'jumps' back and forth quickly while I'm driving (mainly does it when I'm going ~65mph). It'll QUICKLY bounce back and forth between 20,000 and 25,000 psi. the engine was bored over and I put the +75 injectors from CPP (CUMMINS PERFORMANCE INJECTORS). Still has the stock CP3. Also, I feel like it's really bogged down when I'm in 1st and 2nd gear (manual trans). I can lay heavy into the gas from a stop and it just barely moves and doesn't go over 5-10lbs in boost.
Any guesses as to why this might be happening? And think it's safe to drive with it like this?

 

first check your rail pressure wiring for loose or corroded wire! try unplugging the FCA test see what it does then plug it back in how long for recovery? If your not hitting 25k+ then you probably have a leaking cross over tube.

 

Agree with above- what is rail pressure at idle and WOT? any codes? Could need to replace FCA if it is shot it would cause issues with drive ability and pressures. Unplug FCA from back of CP3 and see if it pegs rp and then hook it back up and see how long it takes to recover- try not to leave it unplugged for too long