SEAL 7J7814 - Caterpillar

Illustration 1 g00706426
Fuel Injector Operation (1) Rocker arm. (2) Screw. (3) Pushrod. (4) Lifter assembly. (5) Camshaft. (6) Fuel injector clamp. (7) Fuel injector. (8) Rack.
Illustration 2 g00313984
Fuel injector (7) Fuel injector. (9) Gear. (10) Plunger.When the plunger is at the top of the effective stroke, fuel flows from the fuel supply chamber. Then, the fuel flows around the fuel injector. Next, the fuel flows through the lower port and the upper port of the barrel. As plunger (10) is moved downward by rocker arm (1), fuel is pushed back into the supply chamber through the lower port. Now, the fuel can flow upward through a passage in the center of the plunger. Then, the fuel flows outward through the upper port of the barrel. As the lower port is closed by the lower scroll on plunger (10), fuel can still flow through the upper port. Fuel will continue to flow through the upper port until the upper port is closed by the upper scroll on plunger (10). At this point, fuel injection starts and the effective stroke begins. During the effective stroke, fuel is injected into the cylinder until the downward movement of plunger (10) causes the lower scroll to open the lower port. When the lower port is opened, the fuel pressure is released.The fuel then flows through the center passage of plunger (10). During the remainder of the downstroke, the fuel flows through the lower port. This sudden release of pressure causes the fuel to hit the deflector (spill) with a high force. The deflector (spill) protects the housing nut of the fuel injector from erosion (wear) due to the force of the released fuel. During the return stroke (upstroke), the chamber inside the injector barrel is filled with fuel again.The plunger can be turned by rack (8) while the plunger is being moved up and down by rocker arm (1). Rack (8) is engaged with gear (9) on the plunger. When the rack moves the rack turns the plunger through the gear. The rotation of the plunger controls fuel injection timing and the fuel output of the fuel injector. The rotation of the plunger changes the relationship between the following components:
Scrolls on the plunger
Ports in the barrelBy changing this relationship, the length of the effective stroke can be increased or the length of the effective stroke can be decreased. Also, the timing of the fuel injection is changed.Note: On 3600 Engines (MUI), the timing is not changed by the rotation of the plunger. On some injectors, the timing is changed by the rotation of the plunger. An example of this type of injector is the injector for the 3116 Engine (MUI) (low horsepower).When rack (8) is moved all the way inward against the fuel injector body, no fuel injection takes place during the downstroke of the plunger. This is the FUEL-OFF position. A small amount of outward rack movement is used as a movement of no fuel or OFF position for governing purposes. The distance of