Just bought a 1989 f250 XLT Lariat 4x4 with a 5.8L EFI gas. And like the title says, its got fuel problems.

1) not sure if this is normal or not, but I can hear the electric low pressure pump running when the trucks running.
2) idle tends to get rough when running on the front tank, has stalled out on me at 45mph on the front tank. Switched to rear, and it started back up after about 5 seconds.
3) rear tank has a hole in it somewhere near the top, so I cant fill that tank too much.
4) idles smoothly on the rear tank.

Now to get into the major issues.

5) When I hit the gas gently, it hesitates, sometimes stalls out, and several cylinders cut out if I maintain the higher idle.
6) When I floor it, from a stop, it hesitates, a couple cylinders cut out, but it does go.
7) In park, if I goose the engine and back off immediately, it hesitates, a couple cylinders cut out, revs up, and backfires once or twice, depending on how many times I goose it (in quick succession...).

I have the truck scheduled for a fuel injector cleaning on Tuesday. I'm going to let them know its been sitting since the last snowstorm, probably 4 or 5 months ago, so there is some bad fuel in both tanks, and me being an idiot, I filled both tanks with fresh fuel. So I suspect I wasted a good bit of money on fuel.

I dont know the first thing about sensors and all this electronic newfangledness. I have a good understanding of the mechanics of engines, I rebuilt and modified my 1976 honda cb750 motorcycle engine, but thats purely mechanical, with no O2 sensors etc.

Anyone know what the most probable causes are? The motor has no valve tap or any mechanical ticks or bubbles, it sounds great mechanically!

Joe

 

Have you ran a fuel pressure test?

 

you could have bad pistons