I should also add, I did some research on these injectors and the oil sending unit. The way I understand it, when you turn key on, fpcm sends a signal to prime fuel system. Once that is done, engine cranking starts to bring oil pressure up and this is what keeps pump running continuous is that oil pressure signal.
This almost makes sense with my problems, with fuel pressure around 30psi for example, my pump won’t run, engine starts to crank and injectors don’t open(sounds like they won’t open with less than 50psi initially) once oil pressure starts to come up under engine cranking, fuel pump kicks in, and it starts up.
I think you lost me.
I will be honest, it is really hard to stay in here with you. In your first post you said you changed the fuel pressure regulator on the fuel rail, but your truck doesn't have a fuel pressure regulator on the fuel rail. Then in that same post you said you swapped the fuel pump relay, but your truck doesn't have a fuel pump relay.
The symptoms you describe pretty much land on either the FPCM or the Fuel Pump (which has the fuel pressure regulator in its main assembly), so the two most likely candidates have been replaced.
The only thing I can offer is maybe one of the two components that likely are your problem, when replaced, were not functional. But I will say, it is pretty long odds that the new unit (either FPCM or Fuel Pump) was DOA in the exact same symptom you replaced it for.
The only other thing that is in the mix (from my perspective) is the fuel pressure sensor. I guess it is possible that it is reporting in error, but that is easy to check. Just go down to NAPA and rent a fuel pressure gauge. The rental actually is free, they just charge your card in case you don't return it. After returning it, they credit your account in full. It will take about 5 minutes to verify your pressure sensor is good or bad, using the analog gauge and your ODB scanner.
Good luck.
