Robin America DY30 Service Manual page 34

4. Injection timing and effective starting
When the plunger closes suction port of the barrel, forced
delivery of fuel starts. But fuel is not injected from the noz-
2le.at ence because of contraction of,fuel,'etc.
.
Injection timing of this engine is fixed constant ( 2 3 O before
TDC)
irrespective of engine rpm. On the other hand, in start-
ing, a proper delay from the timing for high speed running
and increased fuel injection is indispensable for effective
starting. For this purpose a notch is made at the plunger
head, w h c h reserves to delay the injection timing by nearly
8" to facilitate starting. (See Fig. 57.)
INSTALLED ONLY TO D Y 3 0
Fig.
57
5. Function of the delivery valve
By the plunger stroke, fuel pressure is raised. And when it becomes higher than the pressure remained in the high pressure
pipe, the delivery valve spring is pushed down and the valve opens.
As
the result, the fuel
in
the
high
pressure pipe is delivered
forcibly.When the plunger lead meets suction port of the plunger barrel, deliveryof fuel ends, and the delivery valve is closed
by the spring tension of the valve. At this time, delivery valve prevents reverse flow of the fuel. Also suction back motion
around the upper part of the plunger sucks back the fuel in the equal amount of the stroke [A] and decreases remaining
pressure in the high pressure pipe. The nozzle jets the fuel clearly off and prevents after dripping. (See Fig.
58.)
!I!
/
DELIVERY VALVE SPRING
D E L I V E R Y V A L V E
ION BACK STROKE
Fig. 58
6. Function of the damping valve
The damping valve is assembled in the end of injection
pump and it reaches the
seat
before arrival of delivery valve
at the seat. The
small
orifice in the valve
is
the passage
of
fuel t o the chamber in the delivery valve holder. Accordhg-
ly, descending velocity of the delivery valve is decreased,
which prevents the negative pressure being produced sud-
denly. As a result, proper injection
is conducted and the
DEL,VERY VALVE
DAMPING VALVE
engine noise is decreased. (See Fig. 59.)
-
31
-
Fig. 59