Fuel Injector: Description and Operation

Injection Nozzle Assembly:

OPERATION
Metered, pressurized fuel from the injection pump enters the nozzle holder at the inlet fitting. The fuel passes from the fitting to the pressure chamber, just above the nozzle seat. When fuel pressure is greater than the opposing spring pressure, the nozzle valve is lifted off it's seat, allowing fuel to flow from the nozzle. When the fuel delivery from the injection pump stops, fuel flow is stopped by the nozzle valve returning to its seat.

A certain amount of fuel seepage between the nozzle valve and body occurs for lubrication. This fuel accumulates in the spring cavity and returns through the return line.

CONSTRUCTION
Injection nozzles are of the inwardly opening, differential, hydraulically operated, pintle-type. The injection nozzles direct a metered amount of fuel, under high pressure from the fuel injection pump, into the engine combustion chamber.

Nozzle
The nozzle consists of two parts; the nozzle body and the nozzle valve. They are lapped to form an extremely close-fitting matched set. The nozzle valve carries an extension at its lowest end, called the pintle, which protrudes through the closely fitting hole in the bottom nozzle face. This construction requires the fuel to pass through an annular orifice.


Nozzle Holder
The nozzle holder retains the nozzle in its correct position in the cylinder head and provides channels for conducting diesel fuel to the nozzle.