Dodge Omni/Horizon/Rampage 1978-1989 Repair Guide

Heated Air Inlet System

Print

OPERATION



All engines are equipped with a vacuum device located in the air cleaner intake. A small door is operated by a vacuum diaphragm and a thermostatic spring. When the air temperature outside is 40°F (4°C) or lower, the door will block off air entering from outside and allow air channelled from the exhaust manifold area to enter the intake. The air is heated by the hot manifold. At 65°F (18°C) or above, the door fully blocks off the heated air. At temperatures in between, the door is operated in intermediate positions. During acceleration the door is controlled by engine vacuum to allow the maximum amount of air to enter the carburetor.



Click image to see an enlarged view

Fig. Fig. 1 The heated air inlet system directs heated air into the air cleaner for better cold driveability

TESTING



To determine if the system is functioning properly, use the following procedures.

  1. Make sure all vacuum hoses and the flexible pipe from the heat stove are in good condition.
  2.  
  3. On a cold engine and the outside air temperature less than 50°F (10°C), the heat control door in the air cleaner snorkel should be up or the heated air position.
  4.  
  5. With the engine warmed and running, the door in the snorkel should be in the down or unheated air position.
  6.  



Click image to see an enlarged view

Fig. Fig. 2 Use a hand pump to apply vacuum to the diaphragm-carbureted model shown

  1. Remove the air cleaner. Allow it to cool to 50°F (10°C), or less. Using a hand vacuum pump, apply 20 in. Hg (68 kPa) to the sensor. The door in the air cleaner snorkel should be in the up or heated air position. If not, check the vacuum diaphragm.
  2.  



Click image to see an enlarged view

Fig. Fig. 3 Fuel injected models can be tested the same way. Simply apply vacuum to the vacuum diaphragm connector

  1. To test the diaphragm, use a hand vacuum pump to apply about 20 in. Hg (68 kPa) to the diaphragm. It should not leak down more than 10 in. Hg (34 kPa) in 3 minutes. The door should not lift from the snorkel at less than 2 in. Hg (7 kPa), and be in the full up position with no more than 4 in. Hg. (14 kPa).
  2.  
  3. If these conditions are not met, replace the diaphragm and repeat the checks. If the vacuum diaphragm performs properly, but proper temperature is not maintained, replace the sensor and repeat the checks.
  4.  

REMOVAL & INSTALLATION



Vacuum Diaphragm
  1. Remove the air cleaner housing.
  2.  
  3. Disconnect the vacuum hose from the diaphragm.
  4.  
  5. Drill through the metal (welded) tab and tip the diaphragm slightly forward to disengage the lock. Rotate the diaphragm counterclockwise.
  6.  



Click image to see an enlarged view

Fig. Fig. 4 Removing the vacuum diaphragm

  1. When the diaphragm is free, slide the complete assembly to one side and remove the operating rod from the heat control door.
  2.  

To install:

  1. With the diaphragm removed, check the door for freedom of operation. When the door is raised, it should fall freely when released. If not, check the snorkel walls for interference, or check the hinge pin.
  2.  
  3. Insert the operating rod into the heat control door. Position the diaphragm tangs in the openings in the snorkel and turn clockwise until the lock is engaged.
  4.  
  5. Apply 9 in. Hg (30 kPa) vacuum to the diaphragm hose nipple and check to be sure the heat control door operates freely.
  6.  


WARNING
Manually operating the heat control door could cock the operating rod and restrict proper operation of the system.

  1. Assemble the air cleaner and install it on the car. Test the operation.
  2.  

Sensor
  1. Remove the air cleaner housing.
  2.  
  3. Disconnect the vacuum hoses from the sensor and remove the retainer clips. Discard the old clips, new ones are supplied with a new sensor.
  4.  



Click image to see an enlarged view

Fig. Fig. 5 On carbureted models, the sensor is retained by two small clips



Click image to see an enlarged view

Fig. Fig. 6 The sensor is retained by one clip on fuel injected models

  1. Remove the sensor and gasket.
  2.  



Click image to see an enlarged view

Fig. Fig. 7 After the retaining clip(s) are removed, pull the sensor from its mouting boss

To install:

  1. Install a new gasket and sensor. Hold the sensor in place and install new retainer clips. Be sure the gasket forms a tight air seal. Do not attempt to adjust the sensor.
  2.  

 
label.common.footer.alt.autozoneLogo