Fuel gauge test process:

Test the voltage at the fuel sending unit. Between the sender wire and the
ground wire. It should be 10.5 volts with the key in the run position. This
checks the complete system except the sending unit itself. If you have 10.5
at the wires you have verified that: 1) continuity to all components, 2) the
gauge is in working order, 3) the voltage stabilizer is in working
order.This only leaves the sending unit as the culprit! However if the
voltage is higher/lower, replace the voltage stabilizer and retest.

Howard