Abstract: A motor-driven regenerative type fuel pump is provided with an overflow mechanism disposed adjacent to a discharge pipe. The overflow mechanism includes a plug hole in a pump housing and a plug member disposed in the plug hole. The pump housing is formed with an axially inclined recess circumferentially extending around the plug member and communciated with an axial groove formed in the plug member. The rate of overflow of fuel and thus the upper limit of the pump discharge can be adjusted by rotating the plug member relative to the plug hole to compensate for any insufficiency of pressure regulating ability of a pressure regulator in an engine fuel injection system. The overflow mechanism further includes an adjustment-locking member attached to the pump housing and the plug member after the overflow-adjustment by the manufacture has been completed.

Abstract: A communication aperture is formed in a wall of a pump chamber for allowing a part of pressurized fuel in the pump chamber to flow into a motor chamber, to thereby cool a motor armature, brushes, a commutator and so on. The aperture is formed inclined with respect to the direction of fuel flowing in the pump chamber. A dynamic pressure component as well as a static pressure component is applied to the inclined aperture with a result that a sufficient amount of fuel flows into the motor chamber even when a discharge pressure of a pump is decreased.

Abstract: A motor driven fuel pump adapted for use with a fuel injection system of an internal combustion engine has a pump housing and an impeller of regenerative pump type rotatably disposed in the housing and provided with circumferential rows of grooves formed in the opposite end faces of the impeller along the outer peripheral edges thereof. The housing is formed therein with suction and discharge ports and cooperates with the impeller to define a fuel pressurizing passage extending circumferentially of the impeller and surrounding the grooved outer peripheral section thereof. The fuel pressurizing passage is circumferentially interrupted by a partition wall disposed between the suction and discharge ports and extending radially inwardly into close contacting relationship to the outer peripheral section of the impeller to prevent flow of fuel from the discharge port toward the suction port.