Gas guage not working

[72steel]

How can I fix this? the needle stays past empty, even with full tank of gas.

[71meangreenc10]

Sounds like the float is full of gas, 2 ways to fix this, remove the old one and take the brass float to a radiator shop and fix it. modify a new style float to fit your sending unit. Thats what im doing, I hate brass floats.

Smitty

[72GMCburban]

try replacing the fuse on the panel under the dash 1st, if its never been changed then it is the one with the purple band. If that does not work then start checking ohm readings, etc...

[ABHaulR]

check the ground wire, mine was off for years. you have to get to the top of the tank to check it. good luck Dwayne

[72steel]

Originally Posted by ABHaulR

check the ground wire, mine was off for years. you have to get to the top of the tank to check it. good luck Dwayne

what is the best way to get to it? I am thinking that is the problem

[bubbaNcolo]

Gas gauges are such that if you ground out the sending unit wire it will go to empty, opening wire will cause it to go past full. This can be tested out by finding wire to tank sending unit back on frame. Turn on ignition. Now attach voltmeter or test light to a bare part of the sending unit wire. You should read some voltage with a full tank of gas and almost zero volts with a empty tank of gas. You can cut this wire and strip off the insulation on the inbound wire, leave it hanging in the air and NOT touching any metal. Gas gauge should be past full. Now ground this bare wire to frame. Gas gauge should go to empty. If gauge doesn't perform this then problem is NOT in sending unit. If gauge works correctly then issue is in sending unit.

You might have a burnt wire near exhaust somewhere along frame, so follow this wire up to the firewall. If you find no damage then you must assume issue is in the dash.

Remove insturment panel but leave it plugged into wire harness and disassemble the covers until you can get to gauge itself. Remove gauge and use a test light or voltmeter to determine which connectors (3) are ground, 12 volts, sending unit feed line. Once you find 12 volts use it to then test and determine which connector is ground and which is the sending unit. Test sending unit connector by grounding wire on frame then open wire to check to make sure you see this at connector. This will tell you that the wire is good.

Now it's been years since I looked at this but I believe that you will see three threaded posts on back of gauge the middle one is the sending unit connector. The other two are ground and 12 volts. You can hook up the gauge to ground and 12 volts and then ground the sending unit connector and look for a empty, remove middle wire and it should go past full. The gauge may move properly but when grounding middle connector you may find that gauge stops short of empty. This is where you will run out of gas if everything is working correctly, you can live with this but really need to replace gauge. If gauge looks good then check connection on the connectors that capture the threaded studs (these can get loose) and printed circuit board connection to the wire harness. Check connection from firewall to gauge connector. If you left wire on frame cut you could ground it and then un-ground it to test wire all the way up to connector.

Plugging gauge back in and retest each connector on back of cluster housing at connectors will verify that when gauge is installed you still have connectivity.