When either tank is full fuel gauge reads 2/3 to 3/4 empty. Hence, I never know when reading "empty" really means, "EMPTY". I have replaced (1) tank sending unit, dash switch and fuel distributor-switching unit with no success. I suspect the gas gauge needs replacing since it indicates both tanks being faulty readings???? Thanks for any input.
Most likely the resistor on the back of the gauge: The GM Fuel Gauge Mystery 1965 & Newer | Pull it off and see if the gauge moves. There are 5 different color resistors, you'll want to replace it with the same color: Lt blue-123 ohms green -89 yellow-88 orange-86 blue black-81 I had one fail on the back of my voltmeter last year, threw me off when I looked down and saw 0 volts. Managed to find a replacement after scouring the local wrecking yard.
