Yanmar 4TNE98, Service Manual

Page: 179 / 246

4TNV98 & 4TNE98 Diesel Engine Section 4. Fuel System 177
End of Injection
Figure 7-14
Figure 7-15
When the plunger is further lifted up by the cam
disc until the cutoff port of the plunger just overruns
the control sleeve, the high-pressure fuel in the
plunger high-pressure chamber returns to the pump
chamber through the cutoff port. As a result, the
fuel pressure in the plunger becomes lower than
the set force of the delivery valve spring, so, the
delivery valve closes to terminate pressure feeding
of fuel.
Uniform Pressure Process
Figure 7-16
Figure 7-17
When the plunger turns a further 180° after the end
of fuel injection, the uniform pressure slit of the
plunger meets the outlet port of the plunger barrel.
As a result, the pump chamber is connected to the
outlet port, thereby making the pressure in the
chamber and outlet port equal. After the uniform
pressure process, the pressure in the outlet port
becomes uniform, ensuring stable fuel injection.
The suction process through the uniform pressure
process are carried out for each cylinder during
every injection cycle.