PLUG (CORE) 3D8818 - Caterpillar

An automatic timing system will increase or decrease the timing of fuel injection depending on engine speed. Timing of the fuel injection is the point when fuel is injected into the cylinder on the compression stroke.The unit functions from approximately low idle up through rated speed. The amount of timing advance is marked on the unit. It is set at the factory and is not adjustable. The automatic timing advance unit is gear-driven and is mounted on the front of the engine camshaft. The drive gear is connected to the camshaft by a spring-loaded carrier. As the engine speed increases, centrifugal force moves the weights outward against spring pressure advancing the point of fuel injection. As engine speed decreases the spring pressure moves the weights inward and the point of injection is retarded.Fuel Limiter (Later Engines)
The hydraulic operated fuel limiter reduces the dark exhaust smoke associated with acceleration with engine speeds below 1200 RPM. After the engine starts and the governor flyweights begin to control the engine speed, the spring will force the piston and rack to the left uncovering an oil passage. Pressure oil enters through the passage filling the compartment to the right of the piston restricting movement of the piston and fuel rack during acceleration. The bleed orifice will drain pressure oil from the compartment after the engine has stopped.