To have fewer moving parts and fewer total
Simple design with compactness.
It can use a simple mechanical governor. No
hydraulic assist required.
The injection pump housing is filled with fuel
oil, rather than crankcase oil for lubrication of
all internal parts.
The plunger, barrel, and sleeve design used in all
Caterpillar sleeve metering units follows a
The transfer pump, governor, and injection
pump are mounted in one unit.
Uses a centrifugal timing advance for better fuel
economy and easier starts.
The term sleeve metering comes from the method
used to meter the amount of fuel sent to the cylindersa
sleeve system (fig. 5-10). Rather than rotate the
plungers to control the amount of fuel to be injected,
like most pump and nozzle injection systems, the use of
a sleeve is incorporated with the plunger. The sleeve
blocks a spill port that is drilled into the plunger. The
3. Fill port
4. Spill port
5. Metering sleeve
Figure 5-10.Sleeve metering barrel and plunger assembly.
amount of plunger travel with its port blocked
determines the amount of fuel to be injected. Basic
operation is as follows:
Fuel is drawn from the fuel tank by the transfer
pump through the fuel/water separator and the
primary and secondary filters.
Fuel from the transfer pump fills the injection
pump housing at approximately 30 to 35 psi with
the engine operating under full load. Any
pressure in excess of this will be directed back to
the inlet side of the transfer pump by the bypass
valve. A constant-bleed valve is also used to
allow a continuous return of fuel back to the tank
at a rate of approximately 9 gallons per hour, so
the temperature of the fuel stays cool for
lubrication purposes and assist in maintaining
Since the injection pump is constantly filled with
diesel from the transfer pump under pressure,
any time the fill port is uncovered, the internal
drilling of the plunger will be primed by the
incoming fuel caused by the downward moving
plunger relative to pump camshaft rotation (fig.
At the correct moment, the rotation of the pump
cam lobe begins to force the plunger upward
until the fill port is closed, as it passes into the
barrel. At the same time the sleeve closes the
spill port. The pump, line, and fuel valves are
subjected to a buildup in fuel pressure and
injection will begin (fig. 5-11).
Figure 5-11.Injection pump operating cycle.