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.