Fuel gauge reads wrong

New to owning a P71. 2006 Interceptor. Tried to fill the car for the first time sense buying this car last week and it only put in 10 gallons from having the fuel light come on. Turned on the car and the gauge only reads to just below 3/4 tank. If I'm not mistaken these cars have a 19 gallon tank. What things can I take a look at to correct this issue. Thank you for your guys insight.

most likely you will have to get a new float in the gas tank

Same problem with my 2007 CVPI. Its a common problem and short of pulling the fuel tank to replace the fuel level sending/float assembly, there's not much you can do. Unless somebody else has a better suggestion?

You can test the gauge.
The range on the sensor is 15(empty)-160(full) ohms

You don't have to pull the tank to get the sender out or to test it, it's mounted just behind the differential with a plug that has wires for pump and sender.
If you just want to throw parts at it, just get the tank as low as possible and pull the pump/level sender, support the frame and let the rear axle assembly hang and you [i]should[/i] be able to get it out.

Thanks guys. I appreciate the info. I'll check it out

Yeah, Thanks! This is my first Ford, and am new to the ways and wonders of some of Fords "Better Ideas'! And yeah, I'm a parts slinger, not an electrical wizard. Whats an OHM meter! lol