Yanmar 4TNV98, Service Manual

Page: 180 / 246

4TNV98 & 4TNE98 Diesel Engine Section 4. Fuel System 178
Reverse Rotation Prevention
Mechanism
Figure 7-18
While the plunger is rotating in the correct direction,
the fuel is sufficiently drawn into the plunger since
the inlet port of the plunger barrel opens during the
plunger lowering process. The inlet port closes
during the lifting process to inject the fuel.
On the contrary, the inlet port of the plunger barrel
does not close during the plunger lifting process if
the engine rotates in the reverse direction. So, the
fuel is not pressurized, resulting in non-injection
state.
Fuel Injection Volume Adjustment
Mechanism
Figure 7-19
The fuel injection volume is increased or decreased
by changing the control sleeve position, resulting in
change of the effective stroke. The effective stroke
represents the plunger’s stroke from the time the
inlet port and inlet slit close until the cutoff port
overruns the control sleeve, which is proportional to
the fuel injection volume. When the control sleeve
moves to the left, the effective stroke (I
2
) decreases.
When the control sleeve moves in the opposite
direction, or to the right, the effective stroke (I
1
)
increases to increase the fuel injection volume. The
control sleeve position is determined according to
the governor control.