Yanmar 4LHA-HTP Operation Manual page 399

Chapter 3 Fuel Injection Equipment
7. Timer Construction and Operation
Load Timer
L
Fig. 51 Load timer construction and operation
The load timer functions to retard injection tim-
ing under partial loads in the low and in-
termediate speed range, and to reduce exhaust
emission and engine noise.
With the load timer, the governor sleeve, the
governor shaft, and the injection pump housing
are specially constructed to facilitate the
escape of fuel oil in the injection pump cham-
ber from the governor sleeve control port,
through a passage in the governor shaft and
pump housing to the low pressure side.
When the flyweights are closed, the control
port and the governor shaft passage are not
aligned.
Governor shaft
Control port
a r
Flyweight
Feed pump
When the flyweights begin to open with an in-
crease in the engine speed, the control port
and the governor shaft passage barely align
and injection pump chamber pressure begins
to decrease as the pump chamber fuel oil
flows to the fuel inlet (i.e. low pressure side)
through this passage. When fully open pres-
sure reduction is complete.
As a result, the timer's advance angle is only
retarded an amount equal to the value of the
pressure reduction.
Furthermore,
sleeve's) position changes in accordance with
control lever position (engine load).
3-1-42
Governor sleeve
Low pressure side
the flyweights'
4LHA SerieA
(governor