To clean the tank, remove the fuel level sensor, rinse the tank with gasoline. Then, with a stream of hot water, the tank is washed and steamed from gasoline residues.
Carefully inspect the tank along the junction line to make sure there are no leaks. If a leak is detected, solder the tank with soft solder. You can only solder a well-washed and steamed tank that does not contain gasoline vapors to prevent their ignition during soldering.