Its hard to find a good schematic of the fuel sender but luckily the fuel sender is pretty straight forward.
- Brown is ground and is attached through the gas tight connector to the main plate
- There is a solder lug on the main plate. The negative lead from the fuel pump goes directly to the solder lug on the main plate.The wiper on the float arm is electrically grounded through the main plate through its pivot.
- White is connected between an etched copper pad on a PCB and a lug on the gas tight connector
- Yellow is connected between one side of the rheostat and a lug on the gas tight connector
- Green/White goes directly to the fuel pump positive lead through a lug on the gas tight connector
If you see open circuit between the brown and tank, the break is likely inside the gas tight connector.
Verification test:
1. Use an alligator clip lead to extend the negative terminal of the pump to outside the tank to be safe against explosions.
2. Test continuity between the extension lead and plate. If you have continuity, the negative lead to the pump is intact. If you have open circuit, likely the negative to the pump is broken off.
3. Test continuity between the extension lead and Brown wire. If you have continuity, the gas tight connector is intact. If you have open circuit, likely the gas tight connector is toast.