FUEL SUPPLY PUMP

PURPOSE:To restrain generation of new vapor and prevent it from generating vapor lock by opening an exhaust port on a liquid sealing part formed to approach an impeller in a casing and decompressing fuel pressure there. CONSTITUTION:A fuel supply pump 10 is devised so that an impeller 17 fastened on it is rotated when a motor shaft 31 is rotated at a motor unit 30. Then, fuel is sucked in groove 18 group formed in the outer periphery of the impeller 17 through an inlet port 21, and after fuel is discharged through an outlet port 23, fuel is discharged into the inside of a housing 11 through an outlet hole 24 and delivered to a fuel injection device through a discharge pipe passage 39. At this time a discharge port 27 is opened and provided on a liquid sealing unit 19 so that vapor not deaerated in a deaerating hole 26 provided on the way of a groove passage 25 is discharged out of the housing 11 from an exhaust port 27 through an exhaust hole 28. At this time, as pressure is lowered at the exhaust port 27, it is possible to effectively exhaust vapor and prevent generation of vapor in the neighbourhood of an inlet port 21.