WHEN I BOUGHT THIS VAN ITS FUEL GAUGE DID NOT WORK. WHEN STARTING THE VAN THE NEEDLE GOES NUTS AND AFTER RUNNING. IT JUST PEGS THE FULL MARK. BUT SOMETIME AFTER DRIVING FOR AWHILE .WHEN I START THE VAN IT WILL STAY ON THE HALF TANK MARK TILL I SHUT IT OFF. WHAT MAKES THIS GAUGE ACT LIKE THIS? THANKS AGAIN.
FUEL GAUGE on 1998 GMC Safari
by cheveronjim in Las Vegas, NV on December 10, 2010
ANSWER by DaveJM , December 10, 2010
The fuel gauge is looking at resistance from your sending unit at the fuel tank to then register on the gauge how much fuel you have. The float in the tank raises and lowers with fuel level. The higher the fuel level, the higher the resistance, and the higher the gauage goes. And the lower the fuel level, the lower the resistance and the lower the gauge goes. This means when it pegs full, you have the highest possible resistance from your sending unit, or wiring, coming to the gauge. In theory, you have a faulty sending unit, or a wiring issue that is apparently intermittent, since you say sometimes it goes to half full. Testing at the sending unit and float is in order to determine the failure. Good luck, Jim!