The function of a fuel injector (Figure ) is to deliver finely divided particles of fuel in the form of spray (atomized fuel) into the combustion chamber to produce rapid and complete combustion



1) Nozzle – The nozzle is attached to the body of the injector. It is the bottom most part of the fuel injector

2) Nozzle valve – It is seated in its seat by the force of the spring. The spring can be loosened or tightened by adjusting the screw. The spring is connected to a spindle, which tries to keep the nozzle valve down.

3) Fuel passage – The fuel from the fuel injection pump enters the fuel through the fuel passage. The fuel passage is cut in the body of the injector.


The high-pressure fuel from the fuel injection pump passes into the injector through the fuel passage. This fuel is collected in the pressure chamber of the nozzle. Due to the high pressure of the fuel, the nozzle valve is lifted off its seat against the spring force causing the nozzle hole to open. The fuel is injected into the compression chamber in the form of fine spray through the hole. When the pressure of the fuel flowing through the fuel passage falls, the nozzle valve is brought back to its seat by the spring force. Thus the nozzle hole is closed.

At the tip of the nozzle there may be a single hole or multiple holes for spraying the fuel.

The fuel injection nozzle helps to deliver the fuel into the combustion chamber and also to atomize the fuel.

See More: Fuel Pump-Construction and Working

See More: Coil Ignition System

See More: Carburettor

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