Yanmar 4LHA-HTP Operation Manual page 416

Chapter 3 Fuel Injection Equipment
12. Fuel Injection Nozzle
12. Fuel Injection Nozzle
When fuel oil pumped by the fuel injection pump reaches
the injection nozzle, it pushes up the nozzle valve (held
down by spring), and is injected into the combustion
chamber at high pressure.
The fuel is atomized by the nozzle to mix uniformly with the
air in the combustion chamber. How well the fuel is mixed
with high temperature air directly affects combustion effi-
ciency, engine performance and fuel economy.
Accordingly, the fuel injection nozzles must be kept in top.
condition to maintain performance and operating efficien-
cy.
(1) Hole type fuel injection nozzle
t'
Applicable engine model-
I. D. mark
Positioning pin-
F.O. return pipe joint
- Nozzle cover mounting groove
Nozzle holder
- Fuel starting pressure adjusting shim
- Nozzle spring
- Nozzle spring seat
-Stop plate
izzle valve
— Nozzle
:zlebodyJ
Nozzle clamp nut
12-1 Functioning of fuel injection nozzle
Fuel from the fuel injection pump passes through the oil
port in the nozzle holder, and enters the nozzle body
reservoir.
When oil reaches the specified pressure, it pushes up the
nozzle valve (held by the nozzle spring), and is injected
through the small hole on the tip of the nozzle body.
The nozzle valve is automatically pushed down by the
nozzle spring and closed after fuel is injected.
Oil that leaks from between the nozzle valve and nozzle
body goes from the hole on top of the nozzle spring
through the oil leakage fitting and back into the fuel tank.
Adjustment of injection starting pressure is effected with
the adjusting shims.
Nozzle holder
Fuel starting pressure
Adjusting shim
Nozzle spring
Nozzle spring seat
Nozzle valve
Nozzle body
Hole
F.O. reservoir
Spray angle
3-1-59
, 4LHA Series
F.O. return pipe joint
Nozzle cover
Positioning pin
Stop plate
Nozzle clamp nut
Nozzle valve
Nozzle body
Injection hole