Classic/Antique Car Repair: fuel gauge 68 Nova, fuel gauge, fuse panel

Question
Hi,  My son has a nice 68 nova, but the fuel gauge does not work.  It is always pinned on full, key on or key off. Where should we start to look?  I was told their is a ground wire somewhere around the license plate light that may rusted. How do we go about finding the problem.  Thanks

Answer
The first place to look is the fuse panel. There should be a fuse marked "INST" or "IGN" or "GAUGES". Check that and all the fuses while you are there. If that fuse is ok then it is off to find the elusive ground wire in the back of the car. It is under the car usually and near the back side of the license plate area. However to check the gauge I usually start under the dash. Get to the back side of the fuel gauge and with the key on check for voltage with a voltmeter at both terminals of the gauge. If there is no voltage getting to the fuel gauge then there is a problem with the wiring or the fuse. If there is voltage to only one side of the gauge then the gauge itself is defective. Then I go to the back of the car and check at the tank unit.