89 F150 w/5.0. Dual tanks. New fuel pressure regulator and in tank fuel pump in the tank i'm using. I hook up a pressure tester to the fuel rail, turn the switch on, the pressure goes up to about 35 then drops immediately all the way down to 0. If the pressure regulator on the fuel rail is working, it HAS to be a fuel injector problem right? This truck is driving me crazy Thanks all

 

So are you just turning on the key without starting the truck? If so that sounds about right as the pump will run for a few seconds and then shut off if the PCM doesn't see the engine turning.

There's a way to jump the fuel pumps at the diagnostic connector to make them run continuous for testing.

 

No, on your truck the more likely problem is with the duel function resovoir/switching valve.

 

Hi! I am turning the key, fuel pump goes on for a second and I leave the key on.

 

Can I just pinch off the return/supply hose to the tank I am not using?

 

That shouldn't make any difference if the switching valve is working correctly. Is the unused tank getting filled with gas?

 

Hi, no it's not filling with gas

 

I should mention the truck had been sitting for years when I got it. Rear tank had white powder so I replaced it and the pump. I never replaced the high pressure pump. Does that pump also have a pressure regulator in it? Someone told me that the exhaust smells like it's running rich. Thanks all