Drain all fuel from the tank
Disconnect the battery
Remove the gas tank from the vehicle
Remove the fuel sender, pump, and any fittings
Rinse the tank with hot water
Add a rust remover or phosphoric acid solution
Agitate the tank to loosen rust
Let the solution sit for the recommended time
Drain the solution completely
Rinse the tank thoroughly with clean water
Neutralize any remaining acid if required by the product
Dry the tank completely with compressed air or heat
Inspect the tank for remaining rust or holes
Repeat cleaning if needed
Apply a fuel tank sealer if desired
Reinstall the tank and components
Add fresh fuel and check for leaks