PURPOSE: To make it unnecessary to change the arrangement of ordinary components such as the main plunger and a delivery valve, etc. of an injection pump for supplying fuel of different kinds and thereby to facilitate the manufacture thereof, by constituting a subordinate plunger so as to operate integrally with the delivery valve in this pump.

CONSTITUTION: A subordinate plunger 5 is inserted slidably into a hole 4a of a body 4 and is actuated onto the side of a delivery valve 7 by a spring 6. With the rise of the main plunger 1, the main fuel pushes up the delivery valve 7 and reaches a fuel injection valve 3 via the main passage 2. On the occasion, the subordinate plunger 5 rises also with the rise of the delivery valve 7,and subordinate fuel is sent under pressure into an injection orifice 3d in a space 3c via a subordinate passage 8 and a second passage 3f. The main fuel is sent into the space 3c in succession to the introduction of the subordinate fuel into the injection orifice 3d.