Abstract: A fuel supply system comprising a main tank for storing a fuel; a subtank provided in the main tank for storing a part of the fuel; a first communication line for communicating the main tank to the subtank; a first pump provided in the first communication line for supplying the fuel from the main tank through the first communication line to the subtank; a first mechanism provided downstream of the first pump in the first communication line for limiting an amount of the fuel to be supplied from the first pump to the subtank and maintaining a level of the fuel to be stored in the subtank; a second communication line for communicating the subtank to an engine; a second pump provided in the second communication line for supplying the fuel from the subtank through the second communication line to the engine; a fuel return pipe for returning an uncomsumed part of the fuel from the engine to the subtank; and a second mechanism for regulating an amount of the fuel to be supplied from the second pump to the engine acc