Intake Air Control System
Intake Air Control System TestCOLD ENGINE
1. Disconnect the air intake duct.
2. With the engine cold, start the engine and let it run for about 5 seconds and stop. The air control door should rise on start-up and remain fully open for at least 3 seconds after stopping the engine.
- If the door rises, the intake air control is OK, reconnect the air intake duct. If performing the inspection on intake air controls only, go on to "HOT ENGINE" for hot engine inspection.
- If the door does not rise, check to see if the door is binding. If the door is not binding but fails to rise, or it rises but fails to stay up for 3 seconds after the cold cranking test, go to step 3.
3. Disconnect and plug the hose leading to the air bleed valve.
4. Crank the engine for approximately 5 seconds.
- If the air control door does not rise or stay open for at least 3 seconds, proceed to step 5.
- If the door rises and stays up for at least 3 seconds, replace the air bleed valve and retest (step 2).
5. Disconnect the vacuum hose from the air control diaphragm, connect a vacuum pump to the diaphragm inlet pipe and apply vacuum.
The air control door should rise and stay up.
- If the door stays up, replace the check valve and retest.
- If the door does not rise or stay up, replace the air control diaphragm and retest.
6. Reconnect the air intake duct.
HOT ENGINE
NOTE: As the outside air temperature drops, the bimetal spring in the bleed valve closes, causing the air control door to rise and allowing pre-heated air into the air cleaner; consistent intake air temperature (approximately 100°F) is maintained in this way.
1. With the engine running and the cooling fan on, disconnect the air intake duct from the air cleaner case and immediately check the control door position.
The air control door should be down.
- If the control door has dropped down to fully close the hot air intake duct: stop the engine and reconnect the air intake duct. Test is complete.
- If the control door has not dropped to the fully closed position, go on to step 2.
2. Disconnect the vacuum hose from the air control diaphragm.
- If the control door now closes, replace the air bleed valve and retest.
- If the control door does not close, correct whatever is causing the door to bind, and/or replace the air control diaphragm. Retest.
3. Stop the engine and reconnect the air intake duct. Test is complete.