1997 GMC Sierra Fuel Gauge not working

1997 GMC SIERRA
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HILANDR
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Electrical problem
1997 GMC Sierra 6 cyl Automatic
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The fuel gauge in my truck has not worked in some time but I have gotten by, by making sure that I fill the tank the same day every week.
My intention for a long time has been to fix it but I keep putting it off.
The gauge reads half full when the engine is off but when I start the truck the gauge moves to full and stays there no matter what the fuel level is in the tank.
Is this a problem with the float in the tank or with the gauge itself?
thanks
Jun 21, 2008 at 11:44 PM
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AIRSOFTSOLDRECN9
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To properly test the guage for operation you will need to remove the dash so you can remove the guage. Using a 12V source (your battery) and a set of alligator clips; connect one wire from the positive side of the battery to a terminal on the back of the guage and then another wire from the other terminal to the negative side of the battery. The gauge should read F (~no resistance). Now disconnect and the guage should read E. If not then replace the guage.

To properly test the sending unit you will need to remove the fuel tank and then the pump and sending unit. Unfortunatly the pump and sending unit are one assembly so they must be replaced altogether. You can test the resistance of the sending unit with a multimeter and actuate the lever by hand at several positions noting the resistance at each level. Call a gm dealership or a local shop and ask for the resistance range for the sending unit. I will try to find what I can for you.

It sounds more than likely that your Guage is bad.

Note: check the voltage on the back of the dash panel circuit board for a proper 12V to your guage. All the guages should be linked together so if you had a voltage problem then they would all be inaccurate. Also be aware that a bad ground caused by copper tarnish on the circuit board can occur so cleaning the contacts on the board with a suitable agent might do the trick altogether.
Jun 22, 2008 at 12:33 AM