PURPOSE: To provide a fuel pump and constituting method therefor in which reworking and scrapping after a general assembly can be preliminarily avoided by preliminarily testing each of a pump action part and a motor part of a modular automotive fuel pump before assembling of the pump action part or the motor part or assembling within a common casing of both of the pump action part and the motor part.

CONSTITUTION: A pump action part 22 and a motor part 18 for each of which a preliminary test is enforced and a common casing 16 having a substantially cylindrical housing provided with a device capable of permanently holding the parts 22 and 18 are made primary components. In the pump action part 22, a pump element 24 such as a two-stage pump is further included.