Double dump single solenoid unit injector

A cam driven fuel injector having a supply port adapted to be connected to a supply or source of fuel and a drain port comprising:

• a body defining a bore;
• a driven or pumping piston reciprocatively situated with said bore;
• metering piston reciprocatively positioned within said bore remote from said pumping piston;
• a timing chamber defined in said bore between said pumping piston and said metering piston;
• a metering chamber defined in said bore below said metering piston;
• a spring situated within a cavity or spring cage remote from said bore;
• a nozzle, having a needle valve, a nozzle passage surrounding said needle valve and at least one flow orifice, said nozzle extending into said spring cage in biasing engagement with said spring to urge said needle valve to close said at least one flow orifice during noninjecting periods;
• first means for supplying pressurized fuel to said timing chamber and to said metering chamber;
• first dump means for permitting fuel within the timing chamber to be dumped therefrom in correspondence with the motion of said metering piston;
• first passage means for transmitting fuel from said metering chamber to said nozzle;
• second dump means for dumping the fuel within said metering chamber to the supply through said spring cage in correspondence with the motion of said metering piston;
• and for stabilizing the pressure force exerted on said nozzle, during the dumping portion of operation, by the fuel within said spring cage with the pressure force exerted on said nozzle by the fuel within said nozzle passage.