Yanmar 4LHA-HTP Operation Manual page 369

Chapter 3 Fuel Injection Equipment
5. Injection Pump Construction and Operation
Control sleeve
Cut-off port > ^ 4 l
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O O O O o
o o o o o
Cross-sectional view
Cutaway view
ig. 12 Plunger operation; end of injection
Equalizing slit
Outlet port J t ^ o o hf
Cross-sectional view
Cutaway view
Fig. 13 Plunger operation; equalizing stroke
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N ^ p l f f i Z ^
3-1-12
End of injection
When the end face of the control sleeve meets
the plunger's cut-off port, the fuel oil in the
plunger (i.e. the pressure chamber), which is at
a much higher pressure than that in the pump
chamber, returns to
through this cut-off port. The pressure then
suddenly decreases, the delivery valve is
closed by the spring, and fuel oil delivery
finishes. These operations occur instanta-
neously. (Fig. 12)
Equalizing stroke
Following the end-of-injection the plunger ro-
tates 180° and the plunger barrel's outlet port
meets the plunger's equalizing slit.
Then, the pressure of the fuel oil in the injec-
tion passage between the plunger barrel's out-
let port and the delivery valve decreases to
that of the fuel oil in the pump .chamber.
This stroke equalizes each cylinder's outlet port
pressure at injection for every revolution,
therefore assuring stabilized injection. (Fig. 13)
The above operations are performed in the
order of injection for each (pump) revolution.
, 4LHA Series,
the pump chamber