Method for injection fuel, with multiple triggering of a control valve

A method for injecting fuel, which is at high pressure, into air-compressing internal combustion engines, the method comprising providing an injection system (1) which includes a compressor unit (2) for compressing fuel and an actuating device (8) for control valves (16, 17) with which the nozzle needle (12) of an injector is controlled, and triggering one or both of the control valves (16, 17) multiple times or in clocked fashion during individual injection phases or during the injection cycle, via a piezoelectric actuator (8), comprising keeping the control valves (16, 17) closed during the starting phase of the engine, at low mm of the compressor unit (2), and providing a brief opening of the valve functioning as a nozzle control valve (17) after the starting phase, wherein by multiple, clocked opening of the nozzle control valve (17), a cumulative injection quantity is furnished.