Patent ID: 7458362

Claim:
A fuel supply system for supplying fuel from a fuel tank to a fuel supply piping, the system comprising: a back pressure introducing passage provided with a pressure regulating orifice; a fuel pump that supplies the fuel from the fuel tank to the fuel supply piping and to the back pressure introducing passage; and a pressure regulator provided with a case, a diaphragm that partitions an inner space of the case into a fuel pressure regulating chamber and a back pressure chamber, a fuel pressure regulating port that communicates the fuel pressure regulating chamber to the fuel supply piping, a back pressure introducing port that communicates the back pressure chamber to the back pressure introducing passage, a relief port that communicates the fuel pressure regulating chamber to the fuel tank, and a relief valve that operates in accordance with a bulging degree of the diaphragm so as to open the relief port when a fuel pressure in the fuel pressure regulating chamber is larger than a relief pressure that bulges the diaphragm toward the fuel pressure regulating chamber and to close the relief port when the fuel pressure in the fuel pressure regulating chamber is not larger than the relief pressure, wherein the relief pressure is adjusted by controlling a fuel pressure in the back pressure chamber of the pressure regulator, and wherein the back pressure introducing passage is communicated with the fuel supply piping, and further comprising a back pressure introducing valve that allows and interrupts a communication between the back pressure introducing passage and the fuel supply piping.