GMC 4000 Series Service Manual page 366

Quantity of fuel delivered per stroke is gov­
erned by variation of the position of the metering
sleeve (5) in relation to the fixed port closing p osi­
tion (Point "A" at which the top of the plunger
covers the intake ports), for as the spill port (3)
on the plunger (4) breaks over the top edge of the
metering sleeve (5), pumping pressure is relieved
down through the center hole of the plunger out into
the sump surrounding the metering sleeve; and fuel
delivery terminates despite the continued upward
movement of the plunger (4).
NO DELIVERY (VIEW A, Fig. 4)
This view shows "no delivery" position. When
the metering sleeve (5) is lowered to its extreme
position "X," the spill port (3) on plunger (4) is
uncovered at the top edge of the sleeve (5) before
the upper end of the plunger can cover the intake
ports. Under this condition no pressure can be
built up even after the ports are closed, hence no
fuel can be delivered. This is also the shut-off
position. Therefore, the upward movement of met­
ering sleeve (5) increases the quantity of fuel
pumped per stroke and downward movement de­
creases the quantity of fuel pumped per stroke,
until the point of zero delivery is reached.
NORMAL DELIVERY (VIEW B, Fig. 4)
As the metering sleeve (5) is moved upwards
to point "Y," Spill port (3) on plunger (4) emerges
above the sleeve slightly later in the plunger
stroke, hence the effective stroke of the plunger is
sufficient to deliver fuel per engine requirement.
G M C S E R V I C E M A N U A L
FUEL INJECTION SYSTEM— TORO-FLOW ENGINE
MAXIMUM DELIVERY (VIEW C, Fig. 4)
toward position "Z," the spill port on plunger (4)
remains covered by the sleeve until relatively late
in the plunger stroke, hence the effective stroke of
the plunger is longer and more fuel is delivered.
Maximum fuel delivery occurs when metering
sleeve (5) is raised to position "Z" to provide ex­
cess fuel for starting.
by engine lubricating oil supplied by engine oiling
system to a fitting on side of pump housing.
lubricate gears, bearings, tappet roller, and other
moving parts, the oil flows by gravity out of the
pump housing and into engine front cover where it
returns to engine crankcase.
driven through gear train enclosed in the engine
front cover assembly. Refer to figure 5 for view
of gear train and timing marks. An inspection
cover on top of the engine front end cover is pro­
vided for access to injection pump driven gear on
all engines. This cover provides view of pointer
and pump drive hub timing mark for use in timing
the injection pump to the engine.
If the position of metering sleeve (5) is raised
FUEL INJECTION PUMP
LUBRICATION
The fuel injection pump assembly is lubricated
After passing through various passages to
FUEL INJECTION PUMP DRIVE
The fuel injection pump assembly is gear
Sec. 6M
Page 355