Yanmar 6CXM-GTE, Service Manual

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(2) Feature
The fuel injection pump supplies pressurized fuel to the
injection 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 there-
fore be adjusted by rotating the plunger.
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 chamber. Fuel
injection ends when the pressurized fuel has been dis-
charged.
This happens when the lead groove lines up with the port,
(as the plunger rises and the pressure in the fuel injection
pipe drops).
A fuel leak return hole is provided in the plunger barrel. This
returns fuel which leaks through the gap between the plunger
and the barrel to the fuel drain sump through the drain pipe,
preventing dilution of the lubricant in the cam chamber.
(3) Injection volume control
The fuel control mechanism is shown in following fig.
The T-shaped flange at the bottom of the plunger is fixed
in the grooves of the pinion sleeve, and the pinion is
engaged to the control rack. The plunger rotates at the
same time as the control rack is moved, adjusting the
effective stroke and controlling the injection quantity.
1) Full injection volume position
When the rack is set at maximum setting, maximum
volume of fuel is discharged. Injection occurs when
the top of the plunger lines up with the intake port in
the barrel. At this time, the lead groove which is posi-
tioned at the widest stroke part, lines up with the dis-
charge port, prolonging the injection time and
increasing the volume of fuel injected.
This setting is normally used for starting and max. out-
put operation.