Pickup 2WD L4-155 2555cc 2.6L SOHC VIN E 2-bbl (1988)
Altitude Compensator: Description and Operation
California Vehicles
Fig. 104 High altitude compensation system (California)
To meet California high-altitude requirements all carburetor equipped vehhicles include a high altitude compensation system, Fig. 104 in addition to the
feedback carburetor system. The high altitude compensation system consists of a high altitude compensator (HAC) and a distributor equipped with a high
altitude advance system. Fuel/air ratio at high altitude is modified by the HAC to be approximately the same value as sea level. The HAC supplies
additional bleed air into the carburetor secondary main fuel well through the HAC and and to the primary main fuel well.
* At low altitude, the HAC opens to allow manifold vacuum to escape from the HAC to atmosphere. The HAC's additional bleed air passage remains
closed and bleed air is not supplied to the carburetor.
* At high altitude, the HAC closes and manifold vacuum is applied to the carburetor. At the same time, the distributor advances the ignition timing.
