GMC 4000 Series Service Manual page 364

W EIGHT SPIDER
W EIGHT
SPRING
DRIVE GEAR
SERVO VALVE
LUBE OIL INLET
are installed the governor weights, governor sleeve,
and inner and outer governor springs. The gover­
nor fulcrum lever assembly is assembled with
pivot pins engaging slots in either side of governor
sliding sleeve. Lower end of fulcrum lever is link­
ed to an operating shaft internal lever at lower
end, and to control unit rod at upper end. Outer
lever attached to the operating shaft is connected
to engine throttle control linkage. When an increase
in engine speed is desired and accelerator is de­
pressed, internal linkage below the governor sleeve
moves the lower end of fulcrum lever rearward,
fulcrum lever pivots on pins at sliding sleeve and
upper end of fulcrum lever is moved forward; thus
movement is transmitted through control rod to
the control unit which ra ises the metering sleeve
on injection pump plunger. Raising the metering
sleeve causes an increase in the quantity of fuel
injected with each stroke of pump plunger.
With accelerator held in the maximum speed
position, engine speed will increase until the gov­
ernor weights acting on the sliding sleeve force
the fulcrum lever rearward. This governor action
causes the metering sleeve position to be lowered,
thereby reducing the quantity of fuel injected with
each plunger stroke and causes reduction in engine
speed. Thus, the governor lim its the engine speed
to the rpm for which the mechanism has been set.
In a sim ilar manner, the governor responds auto­
matically to increase or decrease the amount of
fuel injected to maintain torque output with varying
G M C S E R V I C E M A N U A L
FUEL INJECTION SYSTEM— TORO-FLOW ENGINE
SPLINED SLEEVE
FOLLOW -UP ROD
Figure 2 — Timing Advance M echanism
load conditions. The idle speed adjusting screw is
used to stop the internal lever in a position to pro­
vide desired idle speed.
E xcess Fuel Starting Device
starting purposes, the injection pump assem bly
incorporates a device which automatically changes
the position of the governor stop plate assem bly.
bricating oil pressure is applied to the starting
device piston to hold the governor stop plate in its
normal run position (toward the smoke lim it cam
on upper end of fulcrum lever).
exists, and the governor stop plate moves forward
to a position which perm its the fuel metering sleeve
on pump plunger to be raised above its normal
position, thereby allowing a greater quantity of
fuel to be injected into cylinders for easier start­
ing. As soon as engine is started and oil pressure
begins to build up, the starting device piston is
forced back to end of bore and governor stop plate
assem bly is returned to normal run location.
ing cycle are illustrated in figure 3. The pumping
PUMP DRIVE SHAFT
To provide an increased quantity of fuel for
Under normal operating conditions, engine lu­
When engine is stopped, no engine oil p ressure
FUEL INJECTION PUMPING
PRINCIPLE
The various stages in the fuel injection pump­
Sec. 6M
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