Expert: Roland Finston - 6/28/2011

Question
Roland, My fuel gauge reads slightly below 1/4 tank and the idiot lite does not come on and I'm out of gas. This has happened twice and now I have to use the trip indicator to watch my mileage. What could be the problem?   Thanks

Answer
Hi Jerry,
The chances are if the gauge is functioning normally until you get to about 1/4 of a tank, then the sensor inside the tank is probably not dropping any lower than 1/4 full. It is a float with a variable resistor attached which increases in resistance the lower goes the float. It is probably mechanically restricted from dropping to the bottom. If you want to verify that is the issue you can go to a plug under the dash on the very left side panel where you will see many plugs just below the underside of the dash that go up into a hidden module. There will be four plugs in a row from front to back colored white, white, gray, white.  On that rearmost white plug you will see it has 26 wire pins and the wire numbers should be etched into the plug next to each wire. Wire 22 is dark blue and that is the wire from the fuel sensor in the tank. With the ignition off insert a pin through the insulation of the wire to contact the wire conductor inside. Then measure the resistance between that wire and any nearby ground (shiney metal body surface). When the tank is empty the resistance should be about 940 ohms, when 1/4 full about 760 ohms, when 1/2 full about 550 ohms, and when full about 130 ohms. If it doesn't rise to 940 as you use gas down to empty than that is what is happening. You will need to remove the fuel tank and change the sensor or figure out what is causing it not to sink along with the fuel level. I can copy some pages from the manual that show how to remove the tank and the module that contains the pump and the level sensor. But you need to tell me you email address in a 'private' response as I don't routinely see the qauestioners' email addresses.
Roland
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Roland