fig1 or integrated in the high pressure plunger 8 39 as shown in fig4 as is seen in the detailed views of fig2 and 3 the bypass valve 17 consists of a bypass plunger 19 moving in bypass cylinder 20 the connecting line 18 opens into the space generated by the bypass cylinder 20 such that a front face 25 of the bypass plunger 19 may be subjected to high pressure a restoring force is exerted on the bypass plunger 19 by a spring 21 defining the initial position of the plunger instead of or in addition to the spring 21 the bypass cylinder 20 may be connected to the medium pressure space 5 via a medium pressure line 22 as indicated by the broken line 22 the bypass plunger 19 has a circumferential groove 23 around its middle into which opens a bypass passage 24 establishing a flow connection between the circumferential groove 23 and the connecting line 16 in this variant the bypass passage 24 is formed by a longitudinal bore 24a and a cross bore 24b in the bypass plunger 19 if the front face 25 of the bypass plunger 19 is subject to pressure the control edges 26 and 27 of the circumferential groove 23 will move across an opening 28 in the bypass cylinder 20 which leads to the fuel bypass line 18 as is symbolised by arrow 29 in fig2 this will open the flow path between the bypass passage 24 and the fuel bypass line 18 and the fuel is bypassed in direct dependence on the pressure in the high pressure space 10 bypassing is performed here for a.