An engine injection system for a combined injection of fuel and an auxiliary fluid into a combustion chamber of an internal combustion engine. A fuel injection pump is used for pumping both fuel and the auxiliary fluid at high pressure. The pump communicates with an injection nozzle and, via a magnet valve assembly, with a fluid metering device, which in turn communicates via a metering line with the injection nozzle. Connecting the magnet valve assembly directly to the supply outlet of the fuel injection pump upstream of an equal-pressure valve, and providing a pressure generator in the metering device, given a suitable triggering of the magnet valve assembly, the remaining supply stroke of the pump piston of the fuel injection pump after the end of the fuel injection by the injection nozzle is utilized to generate the requisite metering pressure in the metering device to enable the auxiliary fluid that is to be metered to be stored in the injection nozzle.