Fuel injection system for internal combustion engine

The fuel injection unit for an internal combustion engine includes a piston-type valve element (42) installed in a bore (43) in the control valve body (41), forming a first valve to connect two pressure chambers (60,62). A second valve is constructed as a slide valve formed by a cylindrical end section of the valve element constructed as a throttling section and protruding into a first overflow oil chamber (59). The throttling section dips into the bore in the control valve body during an opening movement of the valve element after a part of the overall stroke.