That unfortunately is not a help. But I would suspect the sender in the tank since the gauge does move with your testing. Hopefully Chevy part was used in the tank! This is the shop manual test, I do not know where you can get the gauge tester, maybe Autozone rents it. Or a tool truck like snap on. FUEL GAUGE 1. Using Gauge Tester (J 24538A). Disconnect feed wire from fuel gauge tank terminal and connect one test lead to wire and ground other lead. Turn ignition on. If gauge responds but not accurately, proceed to step 2). If gauge does not respond, go to step 3). If gauge responds accurately, go to step 5). 2. Remove gauge and check for loose nuts at gauge terminals. If nuts are loose and gauge reads between 1/4 and 1/2 with 90 ohms from tester, tighten nuts and install gauge. If gauge is inaccurate in other ways and/or nuts are tight, replace gauge. 3. Disconnect front body connector. Connect tester to lead that goes to gauge. If gauge responds accurately, check wiring between rear compartment and front body connector. If gauge does not respond, go to step 4). 4. Remove gauge. Check for bad connections at gauge terminal or instrument cluster connector. If connections are good, replace gauge. If bad, repair connections and install gauge. 5. Check rear compartment connector and wires to sender. If okay, replace sender. If not okay, repair wire or connector.
You could buy a 90 ohm resistor and use it as described for the tool and check for the 1/2 and 1/4 reading. Over-full could, by this test mean replace gauge!
Saturday, March 27th, 2010 AT 5:45 PM