What are some of the causes for low fuel pressure at the rail? This started to happen after my trans had failed and went into limp mode. Not knowing what had happen at the time I stayed in it, and made it hit the blow off a couple of times. Changed the fuel filter and took it for a hit. It done fine. Couple days later I make another hit and it acts up. Really only does it in 3rd and got to let off the pedal for it to shift and then it seems to do fine. Put a gauge on it a vacuum at the rail is around 12-15. So it's restricted somewhere. Any help would be appreciated. 06 Lbz

 

How big of a tune ? Fuel filter good ?
Seems like the cp3 pump is weak. A fuel rail plug will band aid issue .

 

it either has restriction between the tank and pump or the injection pump has failed. If in doubt put a 5 gal bucket of diesel on the pump suction side and see if your rail pressure is normal.