92 F150 Single tank. My son bought the truck. He is learning to drive a manual so he didn't drive it much After 2 weeks the fuel pump went out. After replacing the pump, he put about 8 gallon of gas in and the gauge wasn't working. When we pulled it back out and checked the sending unit, we discovered the ground pin loose on the top of the unit. Not being able to find a new sending unit, I just bought a whole new pump and sending unit together. I checked it with an OHM meter and it ranges from about 20 to 160, which from the info I have found , is correct. When we connect the pump and raise the float, the gauge goes to full. When the float is all the way down, it stops at 1/4 tank, never goes below. I'm thinking the bad wiring could have damaged the gauge. If I unplug the pump and check the sending wire and ground, there is 6 or 7 volts. The gauge goes passed full when disconnected. Is there a way to try to force the gauge to Empty? I am unclear as to how the unit sends a signal back to the gauge. If there is power coming TO the sending unit, how does it get back to the gauge? Electrical systems aren't my strong suit!

 

What does the gauge read if you ground the sending unit wire?

 

Here is the diagram for the fuel level gauge and sender in the tank:

Instrument cluster:




Fuel tank motor and level:



On single tank trucks the fuel selector switch is replaced with a jumper plug on connector C268.

 

Thanks for the help. The gauge was bad. Got one from the junk yard and everything seems to be working now...at least the fuel system. LOL