DESCRIPTION
The Thermostatic Air Cleaner/Heated Air Inlet system controls temperature of air entering the intake system. This permits the system to be calibrated leaner to control hydrocarbon (HC) emissions and improve engine warm-up. The system consists of an air cleaner assembly, temperature sensor, heat control door, vacuum diaphragm, duct system and exhaust manifold shroud.
OPERATION
When the engine is cold, intake air is routed across the exhaust manifold shroud. As air flows across the exhaust manifold, it is warmed before entering the air cleaner. The warmer intake air aids the fuel atomization process in the throttle body and intake manifold during cold engine operation. When normal engine operating temperature is reached, vacuum diaphragm shuts off air flow from the exhaust manifold and allows fresh air to enter intake system.
Scheme 36
TESTING
Note. With engine cold, heat control door in air cleaner snorkel should be closed. With engine running at normal operating temperature, door should be open.
- Ensure all hoses are in good condition. Using external vacuum source, apply 20 in. Hg vacuum to temperature sensor. Door should be in open position. If not, check vacuum diaphragm for leaks or restrictions.
- Apply 20 in. Hg vacuum to diaphragm. Diaphragm should not bleed down more than 10 in. Hg in 5 minutes. Door should not lift off bottom at less than 5.5 in. Hg. It should be in full open position at no more than 8.5 in. Hg.
- If vacuum diaphragm does not operate properly, replace it and repeat test. If diaphragm is okay but proper temperature is not maintained, replace temperature sensor and repeat test.
