User Manual

SENR9977 21
Systems Operation Section
Fuel Injectors
g011424 67
Illustra
tion 24
Each fuel injector is held into the cylinder head by a
clamp aro
und the fuel injector. The fuel injectors are
not serviceable but the nozzles can be removed in
order to clean the orifice.
The fuel injection pump forces the fuel to flow under
high pressure to the hole in the fuel inlet. The fuel
then flo
ws around a needle valve within the nozzle
holder which causes the nozzle to fill with fuel. The
pressure of the fuel pushes the needle valve and a
spring.
When the force of the fuel pressure is greater
than the force of the spring, the needle valve will lift
up.
When the needle valve opens, fuel under high
pressure will flow through the nozzle orifices into the
cylind
er. The fuel is injected into the cylinder through
the orifices in the nozzle end as a very fine spray.
When the fuel is injected into the cylinder, the force
of the
fuel pressure in the nozzle body will decrease.
The force of the spring will then be greater than the
force of the fuel pressure that is in the nozzle body.
The ne
edle valve will move quickly to the closed
position.
The ne
edle valve has a close fit with the inside of the
nozzle. This makes a positive seal for the valve.