A fuel injection system for an internal combustion engine includes an engine management system (EMS), a return line connected to a low-pressure fuel system, a common rail for storing and supplying a relatively high-pressure fuel to an injector, and an automatic isolating valve installed between the common rail and the injector. The injector has a nozzle for injecting fuel into the engine. A valve is operated by the EMS and installed between the common rail and the nozzle. A spill valve is operated by the EMS and connected by its inlet to the outlet of the valve and by its outlet to the return line. A check valve is installed between the nozzle and the return line, the inlet of the check valve being connected to the inlet of the nozzle.