My fuel gauge is pinned at FULL despite only half full. Is this the typical failure mode of the fuel pump float? Or is the mode to be pinned on EMPTY?
That usually means that the float is stuck.
Try banging on the bottom of the gas tank with a rubber mallet see if the gauge drops.
Tester
Great idea. I am recalling that the tank was lowered 6 weeks ago in order to replace a brake line. I think the gauge worked after that, but if a plug loosened, would the gauge show empty or full? I presume the float operates a variable resistor. Is Full maximum resistance or minimum resistance?
Could also be a problem with wiring connections between sender and gauge. Esp since tank dropped prior, so wiring may have been temporarily removed for that. Reversed connections or forgot to connect one wire, etc. Might want to fiddle with that a bit first.
Yes, it’s a variable resistor. If you can figure out the resistance ranges you (or shop) can measure the sender’s resistance by disconnecting it from the gauge, and fixed resistors of known value can be used to test the gauge. Not sure if the sender resistances for full and empty are standardized car manuf to car manuf though.