Why does the fuel guage not work?

you could try this first.hold the odometer trip button in,turn the key to run,not start.when the test begins on instrument panel,let go of the trip button.the first thing it should do is a gauge sweep.you may have to keep pushing the button to advance to the next test.if your gas hand does not sweep,or does and goes back to the same place,then the sender is bad.most of the time when the gauge goes crazy or reads wrong,it is the sender float/switch in the fuel tank.it is part of the fuel pump module assembly.your pump is still working.you could use your trip meter on the odometer to keep up with the miles if you know about how many miles you get to the tank full.the other option is to put the new fuel pump module assembly in the tank.