A fuel injection system for an internal combustion system includes an Engine Management System (EMS), a fuel feed pump, a return line, a high-pressure pump, supplying fuel under pressure to a common rail, a hydraulically operated valve forming an outlet chamber connected to the common rail and a control chamber, the valve being designed such that, in its closed position, the valve prevents the flow out of the outlet chamber, and an electrically operated pilot valve. A nozzle with a resilient member that biases the nozzle towards closing is connected to the outlet of the hydraulically operated valve in such a way that pressure at the outlet of the hydraulically operated valve tends to overcome the force of the resilient member and open the nozzle. An electrically operated spill valve is connected between the outlet of the hydraulically operated valve and the return line.