Yanmar 4TNV98, Service Manual

Page: 177 / 246

4TNV98 & 4TNE98 Diesel Engine Section 4. Fuel System 175
Plunger Operation
Figure 7-3
The drive shaft simultaneously drives the feed
pump, cam disc and plunger. The plunger spring
presses the plunger and cam disc onto the roller.
When the cam disc turns by means of the drive
shaft, the face cam moves on the roller to activate
the plunger’s reciprocating operation. When the
inlet port of the plunger barrel being pressed into
the distributor head and the inlet slit of the plunger
overlap, the plunger draws fuel and applies
pressure to it.
When the outlet port of the plunger barrel and the
outlet slit of the plunger align, the high-pressure fuel
opens the delivery valve to be injected into the
engine combustion chamber via the nozzle. When
the cutoff port reaches the control sleeve, pressure
feeding from the plunger is terminated.