Fuel gauge

Hey guys, about a month ago I filled up my 73 and the gas gauge went to full and has stayed there ever since. I probably went through 1/2 a tank with no movement, i filled up again and went through maybe half a tank again and still on full. Whats the best place to start?

i would start by looking at the wiring to see if the wiring is ok if you put the gauge wire to a Ground it will show full. Or it could be that the needle is stuck in the gauge, mine does that some times if i go around a corner with a quarter tank, the needle goes to empty and stay there until i tap the glass gently then it will come loose. But my main guess is that your gauge wire is broken or pinched and therefore is grounded making the gauge show full.

Forgot to say that the wiring to the gauge has a connection in the trunk right around the latch. Try and unhook the gauge wire and see if it changes anything, if not tha gauge itself could be dead. Unfortunatly the rest of the wiring is on top of the gastank and is not accesseble unless you drop the tank, wich can be a Challenge. However it could be a good time to clean an inspect hoses and wiring and even change the sending unit and get the tank cleaned inside and out.

Thanks! I will start there.

You are welcome hope it helps and you find the fault. I hate running out of gas somewhere.

Fuel Gauge Problem Diagnosis This process can be applied to all recent GM cars except those with computerized gauges.

1) Locate the fuel sender feed wire near the fuel tank. You're looking for a single tan colored wire. With the tan wire disconnected at the fuel tank, the fuel gauge should read past full with the ignition on. Wait a few moments as some fuel gauges take a long time to respond. Touch the tan wire from the body to any convenient ground and the gauge should read empty. If not, you have a wiring problem or a bad gauge.

2) If the gauge responds correctly, the gauge and wiring are OK. Next use a multi-meter to measure resistance to ground of the sender wire connection on the top of the fuel sender or the tan wire from the top of the fuel tank.**** If this doesn't check, then sender or wiring on top of the tank is bad or the sender not adequately grounded. Senders are typically grounded by a black wire which is welded to the sender and attached to the body with a sheet metal screw.

Measurements should track the fuel in tank.****

Full - 84-88 ohms

Half ~ 40 ohms, give or take

Empty - 0-2 ohms



3) If the sender checks OK but gauge and wiring don't, clean the connections, reconnect the sender wiring and separate the Fisher connector (located just outboard of the fuse block under the dash). The gauge should then read past full. Ground the tan wire in the dash side of the Fisher connector and the gauge should read empty. If not, you probably have a bad gauge or possibly a dash wiring problem. Go to Step 5.

4) If the gauge checks OK, then make the same resistance checks to the tan wire in the body side of the Fisher connector. If the readings are different than those at the sender, body wiring has a problem and requires detailed inspection. If they look OK, then the Fisher connector is probably dirty. The gauge should then read past full. Ground the tan wire in the dash side of the Fisher connector and the gauge should read empty. If not, you probably have a bad gauge or possibly a dash wiring problem. Go to Step 5.



5) Clean and reconnect Fisher connector, pull the connector off the back of the gauge and make the same resistance checks to the tan wire. If they don't check, you have a dash wiring problem.

If they check OK, your gauge is bad.

Gauges can be bench-checked but this is probably best left to an expert.

Check out the thread I posted in the ELECTRICAL forums. Just went through a similar situation.