So....picked a truck for cheap recently as a crank/no start. Found out it had a cam dowel that let go and bent push rods. I pulled the motor, had the cam keyed, reworked the heads (all new valves), replaced pushrods and rocker assemblies, replaced injectors and some other parts including FPR. Dropped the motor in after reassembly and fired it before filling cooling system. After a little cranking it fired off and after a few seconds cleared up and ran pretty good so i shut it off.Filled cooling system a found a leak and ended up having to take water pump back off and replace pipe oring to oil filter housing. Reassembled, refilled and som bitch wouldn't fire. It has an AirDog and rebuilt stock filter housing with Cat adapter. Threw a scanner on it and actual rail pressure was climbin way over desired pressure but a just barely trying to fire. I disconnected the FPR and it fired off with some cranking so I know it will run. I then noticed it pretty much loses prime as soon as lift pump turns off. I by passed the stock fuel filter to eliminate that but same thing. Pulled new FPR and replaced with original and actuall pressure is right on the money but still wont run. WTF!?!?!?! The oring had split on new FPR so I thought I found pressure and prime issue in one shot but not the case. Im all ears. 
