Alright guys, I have an 88 f150 that I picked up a few weeks ago. When I picked it up, I was told the rear tank pump was dying, and that the front tank sending unit was bad(evidenced by a gas gauge pegging full). The guy had replaced the high pressure pump, and the switch on the dash. The truck ran alright off the front tank, but when I would switch to the rear tank, the pump would be pulsing, and you could hear a bit of a ticking. I replaced the rear sending unit and pump this weekend, and all seemed well. Drove the truck around a bit, but today I started it up, and it was making the same noises again. I shut it down and started it back up on the front tank and let it run a while, came back out to the truck off. I'm looking for some guidance as to where I should start in fixing this issue. Truck is starting to drive me crazy.

 

Any thoughts at all?

 

Took a video today. The pump whined during the entire video, but it doesn't do it all the time. I apologize for the terrible quality.

 

Hey check the tank switching valve underneath where the 2 gas tank lines meet and then go to the engine, if there is something stuck in there or if that motor is burndt up it wont work. and check the fuel filter. and make sure the wirig to the rear pump is good, I had a 90 f250 that had the same problem and the ground wire was broken and would intermintenly make contact, use a test light and make sure you have power and ground

 

Thanks, I'll check into it! PO replaced the switching valve, but called it the HPFP. So I was wondering if maybe that main pump needed replacing. So I will check on the ground to rear tank. I know that the mid tank has a bad ground I believe. Gas gauge pegs full when it's selected. However, when it's selected, everything smooths out and everything seems to function correctly. But after about 15 minutes or so the truck will die.

 

I got a question for you, did you ever check fuel pressure between both tanks? along with the inertia switch under the dash by the brake pedal and did you replace the fuel filter? if it dies off both tanks I would run a fuel pressure test on both tanks running and not running and the inertia switch disables the fuel pumps, if you wanna know if its that cut the 2 wires and butt connect them to bypass the switch. and a fuel filter is only 12 bucks so that's good insurance. good luck!

 

The truck only dies off the front tank, but everything sounds like it's working correctly. Whereas, the truck runs just fine off the rear tank, but sounds like things aren't working right at all.