Boon, the fuel gauge sending unit is located on the fuel pump in the fuel tank of the car. It consists of a float, connected to a thin, metal rod. The end of the rod is mounted to a variable resistor. Take a look [http://auto.howstuffworks.com/fuel-gauge1.htm|on here] about how it works. they are really not that adjustable unless you bend the small metal arm. This will no be very exact. I'd have someone measure the resistance of the unit to see what the values are. The only other thing would be to replace the sending unit.
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