question about fuel sending unit

[gmc67swb]

OK HERE GOES. THE GAS GAUGE READS EMPTY. I PULL THE SENDING UNIT OUT AND IT READS PAST FULL.(WITH WIRE CONNECTED) I GROUND THE SENDER, AND AT THIS POINT I CAN MANUALLY MOVE THE FLOAT ARM UP AND DOWN AND THE FUEL GAUGE READS FULL SWEEP JUST LIKE IT SHOULD. SO NOW I TAKE THE FLOAT OFF THE ARM AND THERE'S NO GAS IN IT. JUST FOR KICKS I FILL UP THE TUB AND PUT THE FLOAT AND SENDER IN AND IT FLOATS. I'VE CHECKED THE SENDER WITH A METER AT BOTTOM IT READS 1.5 OHMS AND AT THE TOP(FULL) IT READS 95 OHMS. I WOULD THINK THIS IS WITHIN RANGE. THE ONLY THING I CAN THINK OF IS THE FLOAT IS HANGING AGAINST THE TANK WALL, BUT HOW DOES IT READ EMPTY? DOES ANYONE HAVE ANY SUGGESTIONS? IF THE FLOAT FLOATS IN WATER IT SHOULD FLOAT IN GAS, RIGHT?