Injection Pump With F.s.p. - Kubota KX080-3 Workshop Manual

WSM KX080-3 Service
First opening pressure
The force of the high pressure fuel delivered by the injection pump acts to push the needle valve up. When this
force exceeds the set force of the first spring, the nozzle's needle valve pushes the first pushrod up and the valve
opens. (First opening pressure is represented by point E in the bottom left hand figure, and point A in the above
figure.)
Second opening pressure
When the first pushrod has been lifted through the pre-lift, it contacts the second pushrod. As the set force of the
second spring is acting on the second pushrod, the combined forces of both the first spring and the second spring
then act on the needle valve, which will not lift unless these forces are overcome.

[3] INJECTION PUMP WITH F.S.P.

The fuel injection pump with F.S.P. (Fine Spill Port)
mechanism is equipped with two functions: speed timer
function and injection rate control function.
The former function works like this. As the rpm is
low, the injection timing gets delayed. This helps cut
down on NOx and operating noise.
The latter function serves to keep down the initial
injection rate and keep up the later injection rate, which
cuts down on NOx and PM as well.
(1) Fine Spill Port (F.S.P.)
(2) Plunger Chamber
(3) Main Port
(4) Cylinder
III-S-84
Engine
A-B : First Spring's Set Force
B-C-D : Combined Force of
First and Second Springs
P1 : First Opening Pressure
P2 : Second Opening Pressure
L : Full Needle Valve Lift
l : Needle Valve Pre-lift
X1 : Cam Angle (<Symbol>×)
Y1 : Injection Rate (mm3/
<Symbol>×)
X2 : Needle Valve Lift (mm)
Y2 : In-line Pressure
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(5) Plunger
(6) F.S.P. Stroke
(7) Leaking Fuel at Initial Fuel
Pressure-Feed Stage
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