Yanmar 4LHA-HTP Operation Manual page 425

Chapter 3 Fuel Injection Equipment
1. Fuel Supply System
1-3 Functioning of fuel injection pump
Operator side
1. Plunger
2. Plunger barrel
3. Lead groove
4. Intake port
5. Delivery valve
The fuel injection pump supplies pressurized fuel to the injec-
tion nozzles through the action of the plunger. The plunger
reciprocates in the plunger barrel with a fixed stroke and is
lapped for a precise fit. A lead groove is helically cut in the
plunger, and this leads to a connecting groove which rises to
the top of the plunger.
The integrate plunger barrel, the plunger barrel and the flange
case for the delivery valve holder, equips a port for intake and
discharge. The injection volume of individual cylinders can
therefore be adjusted by rotating the integrate plunger barrel.
The fuel comes through this port into the plunger chamber, is
pressurized by the plunger, opens the delivery valve, flows to
the fuel injection nozzle through the fuel injection pipe and is
injected into the combustion chamaber. Fuel injection ends
when the pressurized fuel has been discharged. This hap-
pens when the lead groove lines up with the port, (as the
plunger rises and the pressure in the fuel injection pipe
drops).
The control sleeve groove is fitted to the plunger flange. The
control knob of the control sleeve is inserted in the control
rack groove.
The rack controls the plunger, allowing continuous changes
in the volume of fuel injected from zero to maximum. A fuel
Engine side
6. Delivery valve seat
7. Control sleeve
8. Control rack
9. Fuel leak return groove
10. Protector
leak return hble is provided in the plunger barrel. This returns
fuel which leaks through the gap between the plunger and the
barrel to the fuel lines, preventing dilution of the lubricant in
the cam chamber.
Increase fuel volume
Helix
(Lead groove)
Plunger
3-2-3
4LHASer
Intake/discharge
port
- Plunger barrel
Connecting groove