on my 87 f-150 4 wheel drive, my gas gauges dont work right. i can fill them up and they register full. i can drive a long time and then they will drop to empty. no such thing as 1/2 tank or 3/4 etc. my front tank will shut down after it runs awhile. you can hear it humming, but when i switch to the rear tank the humming will stop. i cant figure it out. thank you kindly.
bill

 

It definitely sounds like an electrical issue. Your floats are grounding out somewhere.

 

i have had the truck for 7 years and it has been like this ever since i bought it. both tanks will go to full when i fill them up, , but like i said they stay on full for a long time. when they go down, they go just about all the way to empty the front tank will shut off delivering fuel when it gets hot or runs for awhile. then after a few minutes you can put it back on the front tank and it will run again for a few miles before shutting down again. you can hear a humming when its on the front tank. switch to the rear tank and the humming stops.how do i go about checking the ground or what do i need to do? will replacing both sending units and both fuel pumps in both tanks fix it? i am not a mechanic, but i will try. i am on afixed income so i cant afford a garage. thanks for all the help
bill

 

Doesnt sound like your rear tank is even an issue other than your fuel reading. You could have a wiring problem from your selector switch to your sending unit/pump in the front tank or possibly when your tank starts to get low your pump screen is picking up debris causing fuel pressure loss. The humming your hearing....is that the HP pump on the frame rail running or are you hearing something else?

 

when i change the selector switch from front tank to the rear tank, the humming stops
thanks bill

 

Hopefully somebody comes along with more know how than me bill but I would start by trying to pin point where your humming is coming from. The only thing I could think of is that your hearing your front tank pump running thats why it goes away when you select the rear but thats a long shot IMO. With the truck running it hard to hear any of those pumps running. Plan of Attack...find the humming noise.

 

im sure its the front tank, but i'll try to listen again. thanks
bill

 

yep, the humming is coming from the front tank, i can take the gas cap off and hear it good. switch to rear tank and it quits. crazy????? lol it's driving me crazy. lol thanks for all input
bill

 

Bill. You are aware, aren't you, that each tank has a fuel pump in it? When the front tank is selected, you're hearing the front fuel pump run. (hum) and running on that tank you have problems with the pump shutting down. When you switch to the rear tank, the humming stops, and if I understand you, the truck will run fine. Tells me the rear pump is OK and the front pump has some kind of problem. Fuel level indication is a different problem. I really don't have any ideas there, except to suggest that if you decide to change the pump in the front tank, you can see if a new sending unit makes the level work correctly when the front tank is selected. Changing the fuel pump and sending unit is not a real simple job.

 

ok, thanks guys. i guess i will have the front one changed pretty soon, i will let you all know what happens. thanks
bill