I am work on an 1993 302 (5.0) out of an f150. It turns over, well start to start then not. I hooked an fuel pressure gauge to the fuel rail. when i cycled the fuel pump (turn on the ing to on ) it would pressure up to 20-30 psi then cycle it agin and it would jump to 40-45. I know it should run at 38 psi should that be hit that point and stay cuz it would take about 30 - 50 secs but it would end up at about 10 psi line pressure. meaning it gets up to pressure but then losses it very quicky is it the fuel pump pressure reg or do I have an bad injector the motor has sit maybe ran an hour in a total of 5-6 years. Any help would be a great help and thank you in adivce.

 

I dealt with one doing the same thing recently. It ended up being the fuel pressure regulator. It's easy to verify that by clamping off the return line hose with a pair of vise-grips. If the pressure quits falling off when the pump isn't running, then you've found your culprit.

 

I would agree that fpr would be initial culprit. if the injector is bleeding off you would have gas in the oil.

 

Ok I blocked off the return line at the tank and it runs up to almost 50 psI on the fuel rail. But wont start just replace the fuel pressure reg then? andit will run I have spark at the 5th cyclinder I didn t check any of the other cyclinders. No codes on the computer. Thanks for your guys help