High Altitude Emission Control System

ALTITUDE SWITCH

There is no practical way to field test the altitude switch, except to check that it is in the correct state for the altitude at which it is being tested.

1. Disconnect switch from harness and connect continuity tester to switch.
Low altitude condition (below 2,000 meters/6,600ft), switch should be open (no continuity).
High altitude condition (above 2,000 meters/6,600ft), switch should be closed (continuity w/little or no resistance).

Replace if defective.

High Altitude Solenoid Valve:

HIGH ALTITUDE SOLENOID VALVE

1. Disconnect electrical connector and vacuum hoses from valve.
2. Connect vacuum hose to port "A" of valve and blow into hose. No air should pass through valve.
3. Energize valve by applying 12 volts to electrical connector, and again blow through hose to port "A". Air should now flow through valve to ports "B", "C", and "D".
4. Replace if defective.


IDLE UP SOLENOID VALVE


1. Start engine and idle.
2. Disconnect idle up solenoid electrical connector.
3. Energize solenoid by applying 12 volts. A noticeable change in idle should occur. If there is no change, valve may be defective or carburetor passages may be plugged.
a. Remove valve from carburetor.
b. Alternately energize and de-energize solenoid. Check that valve retracts when energized, and extends fully when de-energized.
4. Replace valve if defective. If valve checks out OK but no change in idle was noted in step 3, see carburetor service procedures under FUEL SYSTEMS.