PURPOSE: To precisely detect the rotational speed of an engine and a reference position, by laying optical fibers opposed to a pulser attached to a drive shaft, and as well by providing a light receiving element for converting the light from the optical fiber into an electrical pulse signal.

CONSTITUTION: A fuel injection pump 1 comprises a drive shaft 2, a feed pump 4 and a plunger 12. Optical fibers 63a, 63b are connected at one end thereof to a light source 60 and a light receiving element 62, respectively, and are opposed at the other end thereof to a pulser 6. The light receivig element 62 receives a light introduced into the optical fiber 63 through the pulser 6 and converts the light into an electrical pulse signal so that a reference position signal is delivered to a control circuit 59 which controls the amount of fuel injection and the like in accordance with the opening degree of an accelerator, the rotational speed of the engine and the reference position. Thus, the rotational speed of the engine and the reference position may be precisely detected in accordance the presence of light.