SERVICE MANUAL
GENERAL
Section 1
The functions of the governor are:
(1)
limit minimum (lo-idle) engine speed, (2) limit
maximum engine speed and (3) maintain smooth speed
control (without stalling, surging or hunting) within the
limits of its regulation throughout the operating speed
range of the engine.
The all-speed governor provides speed control at any
fixed position of the control lever (accelerator pedal).
This provides the vehicle operator with the most
satisfactory driving characteristics. The governor tends
to keep engine speed constant at the level determined by
position of the accelerator pedal and automatically
increases or reduces fuel delivery in response to minute
changes in engine speeds without a significant change in
road speed and without the operator changing position of
the accelerator pedal.
The transfer pump, a single action none positive
displacement plunger type pump, is driven by the
injection pump camshaft.
The transfer pump can supply more fuel than is required
for injection. Excess fuel, utilized for cooling injection
pump, is routed from the injection pump fuel gallery back
to the fuel pump.
NOZZLE
The American Bosch ADB-M type nozzles (Figure 8) are
of the closed differential hydraulically-operated type.
Fuel, under high pressure, flows into the fuel duct in the
body and enters the pressure chamber. When fuel
pressure in the pressure chamber exerts sufficient force
on the differential area of the nozzle valve to overcome
the opposing spring preload, the nozzle valve is lifted,
allowing fuel to enter the nozzle body sac and flow
through the spray holes. The fuel flowing through the
spray holes is atomized as it enters the combustion
chamber.
When the end of the pumping stroke occurs, there is a
sudden drop in line pressure. As a result, the pressure
in the nozzle pressure chamber drops rapidly. Since the
pressure adjusting spring is exerting a downward force
on the nozzle valve and is no longer being opposed by
fuel pressure, the nozzle valve moves downward rapidly
until it seats in the nozzle body - the nozzle is now
closed.
Since there is a slight amount of clearance (controlled)
between the nozzle valve and body, a small amount of
leakage between the valve and body will occur. This
leakage is necessary for valve O.D. and body I.D.
lubrication.
NOZZLE HOLDER
The American Bosch AKN-M type nozzle holder (Figure
8) is a unit which retains the nozzle in the cylinder head
and transfers the fuel from the high pressure tubing to
the nozzle duct. The holder
Figure 8. Exploded View of Fuel Injection Nozzle and Holder Assembly
1.
Holder Body
5.
Valve Stop Spacer
2.
Shim(s)
6.
Nozzle Body and Nozzle Valve
3.
Pressure Adjusting Spring
7.
Cap Nut
4.
Spring Seat Guide
8.
Copper Gasket
CGES-375
Printed in United States of America
Page 6
