High Altitude Compensation System: Description

The high altitude compensating system consists of the Electronic Control Module (ECM), an altitude switch, and a solenoid valve. The altitude switch senses altitude from atmospheric pressure and activates solenoid valve and ECM at high altitude.

The solenoid valve opens an leans air/fuel mixture by introducing air into the carburetor through the altitude compensating ports. The ECM changes the open duty cycle and also leans the air/fuel ratio. The lean mixture reduces HC and CO emissions at high altitudes. At low altitude the altitude compensating system does not operate.