Re: Fuel Gauge Shoots Up To Full

Posted by HH56 On 2016/4/6 9:55:26

Believe you have a 48 so the sending unit is not a pure resistance type. It is bimetal which has a heater working a bimetal strip in the sending unit. The output is an on or off type operation. Fuel level changes pressure on the bimetal resulting in longer or shorter periods between the on/off cycles. The gauge responds by its heater moving a bimetal connected to the needle when on and stopping when off. That makes it hard to troubleshoot. You do not want to leave the gauge pegged or it could burn out.

It is most likely that the sender is the issue but the wire for the sender goes thru a small hole in the trunk floor at the extreme rear near the latch striker. Then continues over the top of tank to the sender. The hole should have a grommet to protect the wire from floor sheetmetal but it could have deteriorated letting the wire short as it goes thru the hole. Check that spot and also the route above the tank where shifting might have pinched it. Otherwise the wire goes overhead above the headliner along with the tail light wires. That length is not too susceptible to damage until it drops out of the left windshield pillar and goes on to gauge. If wire is still the old fabric type a chunk of insulation could have fallen off in that stretch and wire could have touched metal.