ENGINE AR-PRIMARY 5302685 - Caterpillar

Illustration 1 g01203738
Fuel injection cycle
(1) Screw
(2) Rocker arm
(3) Rack
(4) Upper port
(5) Drilled passage
(6) Plunger
(7) Lower port
(8) Injector barrel
(9) Fuel passage
(10) Needle valve
(11) Piston When plunger (6) is at the top of a stroke, fuel flows from the chamber for the fuel supply, around the injector, and through lower ports (7) and through upper ports (4) of injector barrel (8). As the plunger is moved downward by rocker arm (2), fuel is pushed back into the supply chamber through the lower port. Fuel can also go through drilled passage (5) in the center of the plunger, around the relief groove, and through the upper port of the injector barrel. As the lower port is closed by the bottom of the plunger, fuel can still flow through the upper port until the port is closed by the upper edge of the relief groove on the plunger. 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 the plunger allows the scroll (helix) to open the lower port. This downward movement of the plunger also releases the fuel pressure. The amount of fuel