THEORY OF OPERATION - CONTINUED
FUEL SYSTEM - CONTINUED
Fuel amount is proportional to piston
stroke. Effective stroke is proportional to
angle of fuel delivery. A temperature
compensation takes place in ECU in
order to inject precise amount of fuel.
Each fuel injector is fastened to cylinder head by a gland nut on fuel injector holder. Fuel injectors are not service-
Fuel injection pump forces fuel to flow under high pressure to fuel inlet hole. Fuel then flows around a needle
valve within fuel injector holder which causes fuel injection nozzle to fill with fuel. Fuel pressure pushes needle
valve and a spring. When fuel pressure force is greater than spring force, needle valve will lift up.
When needle valve opens, fuel under high pressure will flow through nozzle orifices into cylinder. Fuel is injected
into cylinder through orifices in nozzle as a very fine spray. When fuel is injected into cylinder, fuel pressure force
in nozzle body will decrease. Spring force will then be greater than fuel pressure force in nozzle body. Needle
valve will move quickly to closed position.
Needle valve fits closely with inside of nozzle.
This makes a positive seal for valve.