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F150 ?fuel pump relay

2000 F150 - V8 - 4.6L - reg cab- long bed - 111K. Twice today, the truck had trouble starting The starter engaged fine and cranked, but it wouldn’t start. The second time it happen, I noticed that I couldn’t hear that “humm” which I’m assuming is associated with the fuel pump, when you turn the key to the “on” position (before you turn the key to crank). After several tries and a few minutes, the “humm” returned and the truck started fine. I couldn’t reproduce the problem after the second time it happened and the truck was fine the rest of the day Is the likely culprit here a relay for the fuel pump ? Where would this relay be located.? As an FYI, I hadn’t drove the truck in over a month - I only put ~2K miles a year on it.

The fuel pump relay is located in the power distribution box (fuse box) under the hood. Remove the cover from the box and on the back side of the cover it’ll identify the fuel pump relay.


@ebko87 If you still have the original fuel pump, it’s probably on its last legs.
Not uncommon for a 13 year old Ford truck.
Just warning you.
If you do wind up replacing the pump, do the filter also.

Thanks for the info guys. I’m hoping it’s the relay, but it could very easily be the fuel pump - of course I just filled the tank today too!

If everything’s fine for now, why don’t you just drive the truck a little more often for awhile?
If you notice that this problem occurs more often, buckle down and get a handle on it.
You know that gasoline goes stale over time, right?

If it makes you feel better, just order a new one and put it in. They aren’t very expensive and should be replaced when replacing the pump anyway. I don’t know about a Ford, but on a GM, once oil pressure is established, the oil pressure switch closes the circuit to provide a second power path to the pump in case the relay fails, the engine will stay running. Also, when you turn the switch on and don’t activate the starter, the pump will energize and run for about 5-10 seconds and shut off. You have to turn the key off again for a half minute or so before it will re-energize the pump again. So you may have been mistaken when you thought the pump only ran sometimes. The idea is to build fuel pressure in the fuel rail for starting. Once the car starts, the computer will turn the pump on again. The engine doesn’t care if the pump runs or not to start, only that fuel pressure is there and maintained. (Of course it won’t run long without the pump on.)

Sorry Bing but you’re wrong. The fuel pump only runs for a second or two when the ignition is turned to the run position and then shuts off. You can cycle the ignition switch to the run position for two seconds and then shut it off and immediately turn back to the run position for two seconds to cycle the fuel pump.

This is one way to determine if the anti drain-back valve in the fuel pump is defective. By cycling the ignition switch on and off a half dozen times.


OK, I’ll defer. I’d like to have a talk with the guy that came up with these electric pumps in the tank though.