Hi All, I've got a 91 F150 v8 5.0 that was sitting for a while and I recently got it starting again. It's having a fuel delivery problem and I'm trying to check the electrical system but can't find any good wiring diagrams. Does anyone know of a place I could find one?

So more info on what's happening with the truck, After getting it to start I tried going for a test drive around the block but couldn't make it out of the ally due to the engine sputtering when I would give it gas. The ignition system has been serviced to get the truck starting as well as new fuel filters, the old gas has been drained along with oil and other basic maintenance work. The battery is new as well.
Here's a video of what's happening. If I push the pedal to the floor it revs a little but then starts stumbling. If I pump the gas pedal I can get it to rev a bit higher but it still maxes out around 3000 rpms.
https://photos.app.goo.gl/YXTVtNYsuphmp4B49

Thanks in advance for any help!

 

get you a gauge, check pressure, how long did it sit, months?, years?

 

Already did all that, pressure is low ~18 but did get as high as 23ish which is still bad. Already dropped the rear tank, tested the pump and that's not doing anything. I hard wired it to the battery. I did find a diagram from a Facebook group. Right now I'm trying to figure out why I loose power when testing the inertia switch. I have power in on the green/yellow wire but I tried bypassing the switch with a jumper and when I do that the power drops to nothing.

 

I don’t know how may of these have anything to do with what your doing, but hope they help.

 

If you have dual tanks here is a good diagram for a 1991 model year gas engine trucks:



Since you are getting some fuel pressure that implies power is getting past the inertia switch. Be aware the fuel pump relay is energized for only 1-2 seconds when you cycle the key from the Off to Run position. When cranking the engine or the engine is running the PIP pulses from the distributor trigger the computer to keep the fuel pump relay energized. To mimic that, you can jumper Pins 2 & 6 on the diagnostic port to keep the fuel pump relay energized whenever the key is the run position for testing.


courtesy of Subford

 

Replace the rear tank pump
23 pounds means it is trying to work and the wiring is okay