SERVICE MANUAL
GENERAL
Section 1
METERING
Metering (providing proper amount of fuel to meet engine
requirements
at
various
loads
and
speeds)
is
accomplished by rotating the plunger in its barrel to
change the effective pumping stroke. The effective
stroke is the distance traveled upward by the plunger
from the time the charging port is covered until it is again
uncovered by the lower helix. A short effective stroke
means a small amount of fuel is injected. As effective
stroke increases, the amount of fuel injected increases.
The metering function can be described by observing the
relationship of plunger helix to barrel charging port under
various metering positions as shown in Figure 5.
Figure 5. Helix and Charging Port Metering Positions
1.
Start Position (Charging Port Closed)
2.
Idle Position (Charging Port Closed)
3.
Full Load Position (Charging Port Closed)
4.
Stop Position (Charging Port Open)
5.
Effective Stroke
6.
Charging Port Position
Starting (Excess Fuel)
For starting, plunger is rotated by control rack to a point
where the maximum effective stroke (port closing to port
opening) is obtained. When engine starts, release
accelerator pedal. This rotates plunger out of start fuel
position to decrease fuel delivery.
Engine Operating (Metered Delivery)
At engine operating speeds from idle through maximum
governed speed, the quantity of fuel delivered is
determined by effective stroke (port closing to port
opening) as controlled by the position of the throttle lever
and governor.
Engine Stop (No Delivery)
To stop the engine, plungers are rotated so that vertical
slots (stop slots) are in line with barrel ports. As plunger
moves up and down fuel is transferred back and forth
from top of plunger through vertical slots and into
charging gallery. The ports do not close - thus, no
delivery.
Plungers are rotated to the various metering positions by
the control rack. Rack movement is controlled by the
throttle lever and governor speed.
PUMP FEATURES
Mounting Adapter
A mounting adapter (9, Figure 1) incorporating four studs
attaches to the injection pump housing. Capscrews
through the injection pump drive gear cover secure the
mounting adapter to the engine front plate. Removal of
the timing pointer plug (7, Figure 1) in the adapter is
necessary when verifying or adjusting pump to engine
timing.
The mounting adapter is an integral part of the injection
pump because it contains the timing pointer. During
injection pump calibration, a port closure mark is
stamped on the injection pump hub directly in line with
the pointer. Because the timing pointer is located on the
mounting adapter and the mounting adapter is fastened
to the injection pump housing by the four studs and nuts,
these four nuts should not be loosened.
Loosening the nuts and rotating the pump housing in
relationship to the mounting adapter will change the
relationship of the timing pointer/hub mark which was
established during injection pump calibration.
CGES-375
Printed in United States of America
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