DESCRIPTION
All Chrysler Light Duty Truck models use a heated air inlet system, as part of the air cleaner. System controls temperature, permitting carburetor to be calibrated leaner to control hydrocarbon (HC) emissions and improve warm-up characteristics.
System consists of an air cleaner assembly, temperature sensor, air control valve, vacuum diaphragm, duct system and shroud on exhaust manifold.
OPERATION
When ambient air temperature is less than 50°F (10°C), carburetor intake air flows through shroud, into flexible connector, through vacuum diaphragm and into carburetor.
When temperature rises to operating temperature, vacuum diaphragm shuts off air coming from shroud, and allows fresh air to enter carburetor. When temperature is between minimum and maximum, air will flow through both circuits.
Scheme 45
- Ensure that all vacuum hoses, flexible duct hose and air cleaner duct are in good condition. With engine cold, heat control door in air cleaner snorkel should be up, in heat "ON" position.
- With engine running at normal operating temperature, door should be in down, or heat "OFF" position.
- Turn off engine. Remove air cleaner and allow air cleaner to cool to 50°F (10°C). Using external vacuum source, apply 20 in. Hg (15 in. Hg on 2.6L) vacuum to temperature sensor. Door should be in up position. If not, check vacuum diaphragm for proper operation.
- 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, and should be in full up position at no more than 8.5 in. Hg. On 2.6L engine, test vacuum motor by applying 10 in. Hg. Air control valve should be in up position. If not, replace air cleaner body assembly.
- If vacuum diaphragm does not operate properly, replace it and repeat steps 1) and 2). If diaphragm works correctly, but proper temperature is not maintained, replace temperature sensor and repeat temperature checks.
