Injectors

Fig. 13 Nozzle and Holder Assembly:

The injector Fig. 13 injects the fuel into the combustion chamber. It is controlled by the fuel pressure generated on the effective stroke of the injection pump.
The fuel pressure generated by the injection pump acts in the pressure chamber on the exposed annular area of the nozzle needle. If the fuel pressure is higher than the opposed force of the pressure spring in the nozzle holder, the nozzle needle is lifted off its seat. The nozzle hole is open and the fuel is injected into the combustion chamber. The nozzle opening pressure is determined by the initial tension of the pressure spring in the nozzle holder. The lift of the needle is limited by the annular face underneath the recessed valve stem.
During injection, the fuel takes the following path: Fuel injection tubing; inlet bore; pressure chamber; spray orifices of injection nozzle; combustion chamber. The fuel leaking past the valve stem flows via the leak-off port on the nozzle holder and is returned to the fuel tank through the return line.
After injection of the fuel quantity delivered by the injection pump the pressure spring again forces the nozzle back onto its seat via the spindle and the valve stem. The nozzle is thus closed again until the next lift.