with electrical power is put in the car the gas needle willgo to pass fulland not work.
The gauge is being powered by the fuel pumps power source. To positively prove it, it only happens when you first turn the key on and while its running correct? The fuel level sending unit works off a rheostat resistor which has little or no resistance with the tank full and resistance increases as the tank empties. With less resistance comes less amperage. If its constantly getting 12 volts that is free of resistance then it will show it's a full tank.
Recheck the electrical connection to the fuel pump. Look for corrosion and damage to pins in connectors.
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