Injection Pump

Fig. 15 Fuel injection pump:

The fuel injection pump, Fig. 15, delivers pressurized fuel under the correct injection timing, and controls the amount of fuel delivered according to engine load conditions. The pump is an inline type pump with one plunger per cylinder.

Fig. 16 Fuel injection plunger & control rack:

The pump consists of plunger barrels and plungers. The plungers are driven by a camshaft, reciprocate within the plunger barrels, and deliver fuel under high pressure. The quantity of fuel injected is changed by the control rack. The control rack moves corresponding to a vacuum signal created by the movement of the accelerator pedal. The control rack turns the plungers, changing their effective stroke, Fig. 16, changing the amount of fuel delivered.

Fig. 17 Diesel fuel injection cycle:

The position in which the inlet port is fully closed by the plunger is called the beginning of injection. As the slanted cut on the plunger connects with the fuel inlet port and fuel flows from the vertical hold in the plunger, pressure in the barrel is released. This is called the end of injection, Fig. 17.