Altitude Compensator: Description and Operation

On some models, the governor is fitted with an altitude compensating device. This unit is used to reduce emissions at various operating altitudes. For turbocharger equipped vehicles, the unit senses manifold pressure for fuel correction while in the boost mode.
As altitude increases and air pressure decreases, the amount of fuel injected is reduced. This is accomplished by the altitude compensator moving the rack by means of a push rod, thereby adjusting fuel injection volume.
When the engine is in the turbo boost mode, the rack is moved in the opposite direction, thereby increasing fuel injection quantity.