oholdguy

i have a 92 f150 4.9 5 speed...i can not get it to run thru the key switch it will fire on one cylinder always the same one i have replaced fuel pump relay the ignition module the electronic ignition switch the computer....the fuel rail holds a good 50lb..i changed the rotor and rotor cap plugs and wires......i can pour gas in the intake and it will run good until that gas runs out any and all help would be appreciated ..thanks for reading hope you got a good idea.....Alvin

Chris_1

iTrader: (1)

50 psi is not great. Your truck calls for 45 to 60 psi, so 50 is getting to the low end of things. If that's the key on engine off reading, then it's a problem because when you apply vacuum to the fuel pressure regulator that will drop below the minimum required to work your injectors properly.
If that's the pressure at idle, it's still not great, but may be helped with a new filter.
The symptoms you describe do sound like a fuel delivery issue.
Plugged filter, dirty injectors, failing pump or any combination of those.
Try a new filter, some injector cleaner and check the vacuum line to the fpr for a fuel smell which could indicate a leaking regulator diaphragm.
If none of that helps you may be looking at a new pump.

oholdguy

To Chris I will try the fuel pump reg. thank you