Injection pump with preinjection

An injection pump for a diesel engine including a casing having a cylinder with a pump chamber (4) in which a rotatable and reciprocatable pump plunger (1) operates and to which fuel is supplied through a main release opening (3) during the intake stroke of the plunger (1) and from which fuel is release through said main release opening (3) near the end of the delivery stroke of plunger (1) via a first release groove (5) with a slanting control edge (6) in the outer cylindrical surface of the pump plunger, and with a second release groove (7) in said outer cylindrical surface between said first release groove (5) and the pump plunger upper edge (13) which in a specific rotational and axial position of pump plunger (1) registers with an auxiliary release opening in pump cylinder (2), whereby the upper edge (14) of said second release groove (7) inclines relative to said pump plunger upper edge (13) at an angle whose size is between one-half the size of the angle of inclination of upper edge (6) of said first release groove (5) relative to said plunger upper edge (13) and an angle which is 6 degrees greater than one-half said angle of inclination.