Altitude Compensator: Description and Operation

Fig. 29 High altitude compensation system. 1982-85 4-156/2.6L engine:

This system is used on 1982-85 California models with 4-156/2.6L engine to maintain the correct air fuel ratio at high altitudes.
An aneroid bellows, Fig. 29, is mounted on the body panel in the engine compartment and connected to the carburetor with hoses and is vented to the atmosphere through the top of the carburetor. As atmospheric pressure expands or contracts the bellows, the brass tapered seat control valve regulates the air flow to the main air bleeds.
During high altitude engine operation, the fuel mixture tends to become richer due to low atmospheric pressure. When the atmospheric pressure reaches a predetermined value, the aneroid begins to open, allowing air to enter the main air bleeds. This auxiliary air, in addition to the present air source, provides the system with the proper amount of air necessary to maintain the correct air fuel ratio.
This system supplies varying amounts of additional air depending upon the altitude. When sufficient atmospheric pressure is restored, the valve closes and system returns to its normal operation.