FUEL SYSTEM
Fuel Injection Nozzle Components and Functions
6-26
6LY3 Service Manual
© 2007 Yanmar Marine International
FUEL INJECTION NOZZLE
COMPONENTS AND
FUNCTIONS
When the high-pressure diesel fuel 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 efficiency, engine performance
and fuel economy.
Accordingly, the fuel injection nozzles must be kept
in top condition to maintain performance and
operating efficiency.
This engine uses double-spring nozzles
manufactured by DENSO.
NOTICE: NEVER disassemble the nozzle holder
retaining nut at a Yanmar workshop. Defer
maintenance to an authorized FIE service shop,
which can maintain the DENSO fuel nozzles.
Fuel Injection Nozzle Functions
A double-spring type fuel nozzle is used with this
engine. This allows each nozzle to inject fuel in two
steps.
Fuel from the fuel injection pump passes through
the fuel port in the nozzle body holder and enters
the nozzle body reservoir.
Figure 6-36
Figure 6-36
1 – Nozzle Body Holder
2 – M6 x 1.0 mm
3 – M12 x 1.5 mm
4 – M15 x 0.5 mm
5 – Nozzle Tip Spray Pattern
6 – No. 2 Spring
7 – No. 1 Spring
When diesel fuel reaches the specified No. 1
pressure (lower), it pushes the nozzle valve up to
the pre-lift (held by the nozzle No. 1 spring
(Figure 6-36, (7))
) and is injected through the small
holes on the tip of the nozzle body.
When the diesel fuel reaches the specified No. 2
pressure (higher), it pushes the nozzle valve up to
the full lift (held by the nozzle No. 2 spring
(Figure 6-36, (6))
), and more diesel fuel is injected
at a higher pressure through the small holes.
After the diesel fuel is injected, the nozzle valve is
automatically pushed down by the nozzle spring
and closed.
94
159.2
21.7
46
9.5
17
(1)
(2)
(7)
(6)
(
3
)
(4)
(5)
0005699
