Sleeve Metering Fuel System
The sleeve metering fuel system on some models of
the Caterpillar engine gets its name from the method of
controlling the amount of fuel injected into the cylinder.
This system has an injection pump and an injection
valve for each cylinder. Most injection valves are
located in the precombustion chamber, while the
injection pumps are located in a common housing.
As with other diesel injection systems, proper
operation depends on the quality and cleanliness of the
fuel. Certain applications of the sleeve metering system
have a water separator to remove up to 95 percent of the
water in the fuel.
COMPONENTS. Thc three main components of
the sleeve metering fuel system are designed and
operated differently from earlier Caterpillar fuel
injection systems. These components arc the plunger,
barrel, and sleeve, which arc mated sets (fig. 5-13) and
must be kept together. The plunger moves up and down
inside the barrel and sleeve. The barrel is stationary
while the sleeve is moved up and down in the plunger.
Sleeve position is controlled by the action of the
governor through varied loads to regulate the amount of
Figure 5-13.-Sleeve metering barrel and plunger assembly.
fuel injected. Located in the inlet side of the system is a
priming pump. When you open the bleed valve and
operate the priming pump, air is removed from the
injection pump housing filters and suction lines.
OPERATIONS. The lifter and plunger are lifted
through a full stroke with each revolution of the pump
camshaft. Spring force on the plunger, through the
retainer, holds the lifter against the camshaft through
the full-stroke cycle. The fuel in the housing supplies
the injection pumps and lubricates the moving parts
in the housing. Before the engine will start, the
housing must be charged, as shown in figure 5-14,
Position 1. The sleeve must be high enough on the
plunger to close the fuel outlet (spill port) during part
of the stroke. The chamber fills with fuel through the
fuel inlet (fill port), which is below the level of thc
fuel in the housing.
Injection begins when the rotation of the camshaft
lifts the plunger far enough into the barrel to close the
fuel inlet (fig. 5-14, Position 2). Both the fuel inlet and
outlet are now closed. Continued rotation of the
camshaft (fig. 5-14, Position 3) lifts the plunger farther
into the chamber of the barrel and increases the pressure
on the trapped fuel. This pressure is felt by both the
reverse flow check valve in the pump (fig. 5-15, No. 1)
and the injector valve located in the nozzle assembly
(fig. 5-11, No. 5). When the pressure is high enough to
open the capsule, injection occurs.
Injection ends when the camshaft rotation causes
the plunger to open the fuel outlet, as shown in figure
5-14, Position 4. The open fuel outlet reduces the
Figure 5-14.-Injection pump operating cycle.