My 86 F250 with the EFI 302 has been sitting in my shop for a while now. Rear end is torn apart at the moment, but the truck runs, so I start it and run it every couple days to keep it going until I can get it back together.

Started it this morning (after replacing the starter solenoid) and the truck ran fine, revved good, the whole 9 yards. Tinkered around a little today, all I did to the truck itself was pull out the aftermarket radio the PO had installed (literally just pulled the radio out, unplugged the wires from the radio but did not touch them further), and installed a VHF radio in its place. (Haven't wired it in either).

Put some fresh gas in the truck this evening and decided to start it again and let it run for a bit. When I turn the key to the on position, I can hear the in tank pumps run, but the frame-rail pump is either other running or is barely running (I can't hear it anymore). Truck will Fire up and idle fine, but if I press the gasand Rev it up it will try to die and will backfire through the intake.

I checked the timing, it's a brand new motor with new plugs, wires, and whole distributor. Have a new fuel pressure regulator, new high pressure pump, and new fuel pump relay.

I'm assuming that something is causing my high-pressure pump to not run or barely run and that the lack of fuel pressure is causing my backfiring issue. Any ideas on what the culprit could be?

Sorry about the long post, just wanted all the details out there.

 

What's the battery voltage? The 60 amp alternators take a long time to replenish the starting current, so if you've been starting it and letting it idle the battery may be quite low.

 

Bang on the frame rail fuel pump and see if it will take off and run.

 

Plug the old radio back in and see if the electrical symptoms change; it *shouldn't* matter, but POs have been known to do all sorts of bizarre things. Past that, I'd want a DVOM to go poking around....

 

Haven't been able to touch the truck today.

Went out a few minutes ago to try yall's suggestions and charge the battery. Figured I try it first for the heck of it. Turned the key on and the high pressure pump primed up, Started the truck and its running and revving fine with no backfiring.

I'm guessing I have a short somewhere for the problem to be intermediate, but I'm not sure. This truck likes to keep me guessing.