Fuel Gauge only reads when engine is off

[Twilightcall]

My fuel gauge on my 94' X only reads when the car is turned off. It doesn't read when it is running for some reason. Any ideas? Thanks.

 

[Opera House]

I doubt it reads when off. You are probably seeing the gauge go to a random rest position. These gauges balance magnetic fields so where they stop is random. You likely have a hole in the sender float. Unplug the tank electrical connector and the gauge should go to full.