engages which spring is supported on an annular shoulder 68 of the nozzle support 14 in the illustrated initial position the pressure piece 60 engages on piston 46 whereby its annular collar 64 is speed from the upper front face of cap 48 by a distance h v in this case the distance h v corresponds to a prestroke of the valve needle whereby the valve needle should by subjected to a weaker dampening in a defined range of the operating performance graph than in the remaining stroke the injection nozzle in accordance with fig1 operates as follows at the start of an injection operation the parts assume the position illustrated in fig1 whereby the dampening chamber 62 has its smallest volume the increasing fuel pressure is now fully effective and acts through pressure piece 60 in a throttling manner on the annular face of the piston 46 which is not covered by the pressure piece thus the valve needle 26 is displaced in the opening direction until the pressure piece 60 comes into engagement with cap 48 after reversing of the prestroke h v the operational diagram in accordance with fig3 which illustrates the valve needle stroke h during the injection duration t is illustrated by the partial path a because the dampening chamber 62 enlarges during this operation the movement of the valve needle 26 is.