The below Toyota Hiace Long Range Fuel Tanks are installed in edition to the vehicles standard fuel tank.  

AUXILIARY FUEL TANK SYSTEM:

This system is designed to pump the fuel from the Brown Davis auxiliary fuel tank into the vehicles standard fuel tank. At the flick of a switch, fuel will replenish your vehicles standard tank, which in turn is then fed to the engine. An LED gauge is supplied to show the driver the fuel level of the auxiliary fuel tank at all times. When the auxiliary tank becomes empty an automatic alarm will sound to alert the driver to switch the pump system off. This prevents the pump from continuously running, preventing fuel pump failure. All parts and hardware for installation are supplied.