FUEL SYSTEM

Provided are a fuel injection valve; a fuel supply passage that supplies fuel to the fuel injection valve; a fuel return passage that returns excess fuel of the fuel injection valve; a leaked fuel return passage one end of which is coupled to a connection part between the fuel injection valve and the fuel supply passage, and the other end of which is coupled to the fuel return passage; an inspection hole provided on the leaked fuel return passage, and that is openable and closable by a plug member; and a check valve provided on the leaked fuel return passage, and that prevents fuel from flowing to the connection part side.