Fuel injection system for an internal combustion engine, method for injecting fuel, as well as an internal combustion engine

The invention relates to a fuel injection system (1) for injecting a fuel (2) into a cylinder (3) of a reciprocating internal combustion engine, in particular two-stroke large diesel engine. Said fuel injection system (1) includes a fuel injector (4) comprising an injector control means (41) for controlling the injection of the fuel (2) into the cylinder (3). The fuel injector (4) is fluidly connected by means of a high pressure pipe (5) to an outlet (62) of a pressure amplifier (6), and the pressure amplifier (6) has an inlet (61) for receiving the fuel (2) being provided under a low inlet pressure (PL) and transforming the low inlet pressure (PL) of the fuel (2) to a high outlet pressure (PH) being provided at the outlet (62) of the pressure amplifier (6). According to the invention, the pressure amplifier (6) is connected to and driven by a hydraulic servo oil (7) being provided under an intermediate pressure (PI) being higher than the low inlet pressure (PL) and lower than the high outlet pressure (PH). Furthermore, the invention relates to a method for injecting a fuel (2) into a cylinder (3) of a reciprocating internal combustion engine as well as a reciprocating internal combustion engine, in particular two-stroke large diesel engine.