Around 3 weeks ago, my '91 F50 (5.0/E4OD/only has rear tank installed) developed a pretty pronounced part throttle miss. I parked it for a time being, and only drove it on 2-3 trips of a mile or 2 on the weekend following the development of the miss (I thought it may have been water intrusion causing the miss, as it had been raining when the miss first developed). After this, the truck sat for 2 weeks.
Today, I went to start the truck and I notice that I don't hear the normal priming of the fuel pump. Thinking I may have missed the priming, I try to start it, but it just cranks and cranks. FP tester confirms there is no pressure at the rail.
The odd part is, while messing around with the ignition trying to get the pump to prime, I notice the fuel gauge pegs max and then settles at the actual fuel level. Once the gauge settles at the fuel level, the motor will cough briefly so it seems like the motor gets some fuel. I have read that the maxing out the fuel gauge can be caused by the gauge not being grounded properly (with the front tank removed, that is what happens when switched to the front). But with the gauge maxing out and leveling off on the rear tank, could this be an issue other than the pump?
If your truck has rust, but everything was working good before, I would check the ground straps from frame to body first. then move on the checking the wiring for the fuel system. Hopefully something simple and you don't have to drop the tank for a new pump.
Thanks for the replies. I will be checking the fuel selector switch and wiring this weekend.
The truck isn't terribly rusty. The frame is basically just surface rust, and the body has the typical rust holes at the top of the wheel wells on the bed, but that's pretty much it. Everything had been working fine for over a year and 10K miles since I bought the truck. I did have an issue with bad grounds that would cause starting issues when the truck was hot, so I added a bit of 1/0 wire for grounds in a few places. It didn't fully resolve the issue, but did make it a good deal better. I'll pick up more cable this weekend and add that as well.
Unfortunately I don't know much about the history of the truck, so I have no idea of the exact mileage or if the rear pump has ever been replaced. Perhaps I should just plan to change it anyway just to be on the safe side.