Hi gang,

I am having problems with my fuel gauge and need help.

My fuel gauge reads 2 o-cock position on the fuel gauge, past the full mark. I am not sure if this is a fuel gauge/dash board problem or a fuel sending unit/in the fuel tank problem.

I checked the ground wire, coming from the fuel tank sending unit and it seems securely gounded.
I noticed that the fuel needle moves a little if I am turning on the ignition from the off position.

So how can you tell if the fuel gauge is bad or fuel sending unit in tank?

Kent :confused:

the gauge will go to full or even past full if the wire comes off or breaks going from tank to gauge
could also need the ground cleaned by the tank
doubt if it is the gauge
sender may be bad but you should check and clean connections first
if you touch the sender wire to ground that will make gauge read empty

Kent,

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. Measurements should track the fuel in tank.

Full - 84-88 ohms
Half - 40 ohms, give or take
Empty - 0-2 ohms

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.

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.

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 best left to a specialist.(Credit for this goes to Fred Aldrich)


Rocky