Yanmar 4LHA-HTP Operation Manual page 366

Chapter 3 Fuel Injection Equipment
5. Injection Pump Construction and Operation
Regulating Valve
Fuel inlet
Fig. 8 Regulating valve operation
Regulating
valve
Spring
Piston
Feed pump
outlet port
3-1-9
Feed pump fuel oil delivery pressure increases
proportionately with an increase in injection
pump speed.
However, the total fuel oil injection quantity
necessary for the engine is considerably less
than that delivered by the feed pump. There-
fore, in order to prevent an excessive increase
in the pump chamber pressure caused by the
excess fuel oil, and to adjust the pump cham-
ber pressure so that it is usually within the spe-
cified limit, a regulating valve is installed near
the feed pump outlet. The timer performs tim-
ing control using the pump chamber pressure,
which is regulated by the regulating valve.
, 4LHA Serit