Post
by road chicken » Sat Apr 14, 2012 1:07 pm
if the rest of your gauges work, you can test the fuel gauge by grounding the wire at the tank connection.
Go under the car on the passenger side, behind the rear wheel. Follow the fuel line to the tank. There is a wire that connects to the sending unit, ( blue for 71, should be the same for you. Make a jumper wire and connect it to ground. then hop back in the dr seat and turn the ignition swith to on. If the gauge is working the needle will swing to way over "full".
Sometimes it is easier to disconnect the wire from the fuel sending unit stud and then gently pop the grommet from the trunk floor and pull it into the trunk, then hook up the jumper wire to ground. There isn't much space under the car on thatside with the exhaust. just be easy on the grommet as they tend to harden up over the years.
IF the gauge swings to 3/4 or not at all, then it is the gauge. Drop me a line if it is, I have a few floating around if it's the standard Rallye pack.
If it goes past full, the gauge and wiring are fine , and that leaves one of two possibilites. The Ground Strap or the sending unit in the tank.
The ground strap is a jumper from the sending unit to the body and completes the circuit. It is right by the hose coming out of the tank. It clips onto the gas line coming out of the tank and clip on to the gas line on the car, basically jumping the hose.. These have a tendency to corrode and rust over the years and they need to be cleaned up and re attached with a little grease to keep the corrosion down, any greas e will do and just a light coating.. If it is broken or otherwise unusable there are replacements availible .
If that doesn"t do it It could be the sending unit. The sending unit should read , on a volt ohm meter, anywhere from 10-ohms at full to 90 ohms empty. That can be checked at the dash wiring between the fuel sending wire and body ground, ( Blue on 71, should be the same on 74 i would think).
Good luck and let us know if that works, or what you are seeing.
4th generation B bodys- there is no substitute.
68 383, Street Demon 750, RPM top end,484/284/108 poo poo cam "-5 spd 4:10 SG, 4whl disk, Helwig Anti-Sway, Poly bushings,Firm Feel Box, HD Linkage, 1" t-bars, 7 leafs Springs
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