The fuel injection system has a fuel injection valve (12) with an injection valve member (34), by which at least one injection opening (36) is controlled, and the injection valve member (34) is acted upon by the pressure prevailing in a pressure chamber (44) of the fuel injection valve (12) and is movable by this pressure, counter to the force of a closing spring (48) disposed in a spring chamber (50), in an opening direction to open the at least one injection opening (36), and fuel is delivered under high pressure to the pressure chamber (44) by a high-pressure fuel pump (10) for a fuel injection. The injection valve member (34) is urged in the closing direction at least indirectly by the pressure prevailing in a spring chamber (50) of the fuel injection valve (12). The pressure in the spring chamber (50) is variable; the spring chamber (50) has a communication with a pressure source (66; 20), which is controlled by a valve (67). Thus different opening pressures of the fuel injection valve (12) for a preinjection and a main injection of fuel can be attained.