Abstract: A fuel injection pump designed to deliver an amount of fuel divided into a pilot and a main injection volume, including a surface of a pump plunger which is guided within a pump cylinder, apart from two recesses limited by an inclined control edge, a first horizontal control edge is formed by a frontal shoulder; and on a side opposite the shoulder, it has a fully enclosed transverse groove with a second and third control edge. Two control apertures and an annular groove above them in the wall of the pump cylinder effect the control, in conjunction with the aforementioned control edges, of the precisely determinable pilot injection and, after a delivery interval, determined by the difference (b-a) between the width (b) of the transverse groove and the distance of the annular groove to the control aperture, the subsequent main injection.

Abstract: A fuel injection pump for internal combustion engines is proposed, in which to attain particularly quiet operation of an engine that is operated with direct injection, the fuel delivery is subdivided into a preinjection and a main injection; this injection is attained by annular groove, coinciding with one another, on the pump piston and pump cylinder, and a connecting groove connecting the coinciding annular grooves with a relief opening. After a partial stroke in the region of coincidence of the annular grooves with one another, the communication with the relief opening is interrupted again. The preinjection quantity can be kept particularly small here, with a short interval between the preinjection and the main injection; in combination with a two-spring-holder injection valve, this particularly small preinjection quantity can be kept constant to a great extent even at varying engine speeds, to attain an optimal reduction in combustion noise at various engine speeds.