Fuel injection system for internal combustion engines

A fuel injection system for an internal combustion engine, comprising a substantially cylindrical injector body having a cylinder which has an engine driven delivery plunger slidable therein, an injection plunger which is hydraulically actuated by the delivery plunger and which defines at its one end an injection pump chamber, a timing plunger which defines, at its one end, a timing pump chamber selectively connected to a drain and which is hydraulically actuated by the delivery plunger to control the connection of the timing pump chamber to the drain, means for feeding the fuel into the injection and timing pump chambers, and nozzle means for injecting the fuel delivered by the injection pump chamber, said injection plunger and timing plunger being axially displaced by the fuel fed into the respective pump chambers, in directions opposite to directions of the movement of the two plungers caused by the delivery plunger, through a stroke in proportion to the amount of the fed fuel, the fuel being delivered from the injection plunger into the nozzle means when the timing plunger causes the timing pump chamber to be disconnected from the drain.