VALVE 8N0014 - Caterpillar

Fuel Injector
Illustration 7 g00322846
Fuel Injector Operation (1) Screw. (2) Rocker arm. (3) Clamp. (4) Control rod. (5) Rack. (6) Drilled passage. (7) Upper port. (8) Lower port. (9) Plunger. (10) Barrel. (11) Fuel passage. (12) Needle valve. (13) Lifter assembly. (14) Camshaft. (15) Piston.The fuel injector is held in position by clamp (3). Fuel is injected when rocker arm (2) pushes the top of the fuel injector downward. The movement of the rocker arm is controlled by the camshaft through lifter assembly (13) and control rod (4). The amount of fuel that is injected is controlled by rack (5). Movement of the rack causes the rotation of a gear that is fastened to plunger (9). Rotation of the plunger changes the effective stroke of the plunger.Injection timing is a product of two factors. The two factors include the angular location of camshaft (14) and the location of plunger (9). The angular location of the camshaft is controlled by the camshaft drive gears at the rear of the engine. The location of the plunger can be adjusted with screw (1) .Fuel Injection Cycle
When the plunger is at the top of a stroke, fuel flows from the chamber for the fuel supply, around the injector, and through the lower ports and through the upper ports of barrel (10). As plunger (9) is moved downward by rocker arm (2), fuel is pushed back into the supply chamber through lower port (8). Fuel can also go through a drilled passage (6) in the center of the plunger, around the relief groove, and through upper port (7) of the barrel. As the lower port (8) is closed by the bottom of plunger (9), fuel can still flow through upper port (7) until the port is closed by the upper edge of the relief groove on plunger (9). At this point, injection starts and the effective stroke of the plunger begins.During the effective stroke, fuel is injected into the cylinder until the downward movement of plunger (9) allows the scroll (helix) to open the lower port. This downward movement of plunger (9) also releases the fuel pressure. The amount of fuel that is injected during the effective stroke is determined by the position of the scroll in relation to the lower port.Fuel goes through the center passage (6) of the plunger and fuel goes through the lower port (8) during the remainder of the downstroke. As the lower port is opened, the sudden release of very high pressure causes the fuel to hit the deflector for spills with a high force. The deflector for spills gives protection to the injector housing from erosion because of the force of the released fuel. On the return stroke, the injector barrel is filled with fuel again from the fuel supply chamber.The plunger can be turned by rack (5) while the plunger is moved upward and the plunger is moved downward by rocker arm (2). The upper part of the plunger has a flat side that fits through the