Automatic Altitude Compensating Device
The governor is equipped with an altitude compensating device to control emissions at various altitudes. On turbo models, the device is connected to the intake manifold to sense boost pressure variations as well.
As altitude increases, air pressure decreases, the push rod in the compensator moves downward and pushes the main rack, slightly decreasing the amount of fuel injected (leans out the mixture).
When the turbo is operating under boost, the rack is pushed in the other direction and more fuel is injected. Injection pump and governor operation are affected by the compensator when the vehicle is operating near sea level or idle RPM.