Fuel Injection Nozzle - Yanmar 4LHA-HTP Operation Manual

Chapter 3 Fuel Injection Equipment

7. Fuel Injection Nozzle

7. Fuel Injection Nozzle
When fuel o i l pumped by the fuel injection pump
reaches the i n j e c t i o n nozzle, it pushes up the nozzle
valve (held d o w n by spring), and is injected into the
combustion c h a m b e r at high pressure.
The fuel is a t o m i z e d by the nozzle to mix uniformly
with the air i n the combustion chamber. How well
the fuel is m i x e d with high temperature air directly
affects c o m b u s t i o n efficiency, engine performance and
fuel economy.
Accordingly, t h e fuel injection nozzles must be kept in
top condition t o maintain performance and operating
efficiency.
7-2 Type/construction of fuel injection nozzle
(1) Hole type fuel injection nozzle
Identification M a r k
Nozzle valve
Dowel pin -
Nozzle body-I
F.O. return pipe joint
• Nozzle cover mounting groove
•Nozzle holder
- Fuel starting pressure adjusting shim
Nozzle spring
Nozzle spring seat
Stop plate
- Nozzle
- Nozzle damp nut
7-1 Functioning of fuel injection nozzle
Fuel from the fuel injection pump passes through th<
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 ij
injected through the small hole on the tip of the nozzk
body.
The nozzle valve is automatically pushed down by th€
nozzle spring and closed after fuel is injected.
Oil that leaks from
nozzle body goes from the hole on t o p 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
3-2-43
4LHA Seri,
between the nozzle valve anc
F.O. return pipe joint
Nozzle cover
Dowel pin
Stop plate
Nozzle nut