Abstract: A fuel pump includes an output shaft of a motor and an impeller configured to rotate integrally with the output shaft. An outer periphery of the output shaft includes a first flat portion for engaging with the impeller. The impeller includes a through hole at a center thereof, the through hole being larger than an outer diameter of the output shaft and including a second flat portion for engaging with the output shaft. In this fuel pump, when the output shaft and the impeller are arranged coaxially, spots exist which have different lengths of a gap between the first flat portion and the second flat portion in a rotational axis direction of the output shaft.

Abstract: Fuel pump (10) may comprise a casing (18) and a substantially disc-shaped impeller (20) which is rotatably disposed within the casing (18). A first group of concavities (21a) may be formed in a lower face of the impeller (20). A second group of concavities (20a) may be formed in an upper face of the impeller (20). A first groove (30) may be formed in the inner face of the casing (18) opposite the upper face of the impeller (20). The first groove (30) is formed in a region opposite the first group of concavities (21a) and extending from an upstream end to a downstream end. A second groove (24) may be formed in the inner face of the casing opposite the lower face of the impeller (20). The second groove (24) is formed in a region opposite the second group of concavities (20a) and extending from an upstream end to a downstream end.