Unit injector for a diesel engine

A unit injector for a diesel engine comprising, a main body comprising a cylinder, said cylinder having a large diameter portion and a small diameter portion, a servo-piston slidably fitted in said large diameter portion and a pump plunger connected with said servo-piston and slidably fitted in said small diameter portion, a pressurizing chamber being formed between the large diameter portion and the tip of said servo-piston, an injection nozzle connected at the end of said small diameter portion, a pump plunger chamber in communication with said injection nozzle and formed between said pump plunger and said injection nozzle, a fluid element and a spool valve body, said spool valve body being connected with said pressurizing chamber, means for supplying fuel under pressure to said fluid element, said fluid element having at least two outputs for selectively directionally controlling the supplied fuel, means to effect the injection stroke of said pump plunger when the fuel is supplied from one output of said fluid element, said spool valve being actuated by the supplied fuel pressure from another output of said fluid element to discharge the fuel in said pressurizing chamber and to supply the discharged fuel into said pump plunger chamber.