Abstract: A fuel pump apparatus having two-stage pump sections and a vapor discharge port. A first impeller of a first stage pump section is attached to a vertically lower surface of a second impeller of a second stage pump section, the second impeller having a larger diameter than the first impeller. A vapor discharge port is formed in the second impeller at a radially inward portion thereof to open to a radially inwardly portion of a first pump passage. Fuel vapor is separated from liquid fuel at the first stage pump section and the liquid fuel is pressurized at the second stage pump section.

Abstract: A pump apparatus of a regenerative type having a vapor discharge port for avoiding a vapor lock. A portion of a circumferential fluid passage of a pump is enlarged within an angular range of 180.degree. measured from a suction port of the pump and the vapor discharge port is formed at a downstream end of such an enlarged fluid passage, so that fluid flow speed flowing through the enlarged fluid passage is relatively slow and vapored fluid can be effectively exhausted out of the fluid passage.