Unit Injector for Staged Injection

A unit injector for staged injection of fuel in an internal combustion engine is disclosed. The unit injector comprises a fuel pump and a spray nozzle combined in a single unit adapted to be mounted on the engine with the fuel pump adapted to be driven by a mechanism provided on the engine. The fuel pump of the unit injector includes a pair of cooperating plungers defining first and second fuel compression chambers for producing a plurality of discrete fuel injections during a single cycle of the internal combustion engine and with a single stroke of the driven plunger of the fuel pump.