I have a 1988 f150 4x4 that im fixing up and im having issues with the fuel gauge. When i first got the truck the gauge was working but when the truck was off it would always sit between 1/4 tank and half a tank. so since the bed was off repainting it i replaced the fuel pump assembly in the tank and ever since then the fuel gauge is still sitting on half a tank when the truck is off but is pegged out past full when you turn it on. i got the truck near empty recently and the gauge was barely touching F so filled it up and its still doing the same thing (way past F). I see there are threads that have similar topics, but all them are saying its pegged out on full even when truck is off mine is not the case. i know the float is working fine cause it moved smoother than the older one i took out. any ideas?

 

I believe pegged full means your sender wire is shorted to ground (going from memory here). First thing to do is pull the connector off the pump and then see what the gauge reads. If it's still showing full, ground the sender wire and see what it does.

 

okay so I unplugged the wire and its pegged out further past full. Do you know which wire is the sender wire?

 

Single tank ?
Fuel Gauge Sender is Yellow/White stripe
Pump is Pink/Black stripe
Black is ground for the Sender
Orange is ground for the Pump

 

great thank you and yes it has a single tank. Do you know what the orange wire is for? Mine has all those colors plus the orange wire going into it.

 

Oh yeah, that is a ground wire as well, for the Pump.

 

Alright when I get a chance I'll test them with a volt meter or a test light and let yall know what happens.

 

Alright so I grounded the yellow wire to my shock. I know its not probably the best ground but I just wanted to see what would happen and the fuel gauge moves to 3/4 of a tank. Idk what that means or if it means anything lol.

 

Also even with the wires being unplugged from the tank and the ignition off and keys out it stays on half a tank.

 

I would expect the reading would change after installing a new sender.
I think you have a problem with the fuel gauge.

 

Okay great thank you. I'll give that a shot and let yall know if it fixes it.

 

do you mean replace the sender in the tank or the gauge behind the dash?

 

Okay so I bought a new sender and it's doing the same thing. The sender in the gas tank is reading 2 ohms for some reason. So I guess that means I gotta take the bed back off and see what wrong with the new fuel pump.

 

In the dash.