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Home >> Jeep >> 1981 >> Cherokee Laredo, 2D Utility, 4.2L Eng VIN C, AWD >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Thermostatic Air Cleaner >> Testing >> Trap Door
July 1: So it begins. Don't worry, this is not in the correct legal jurisdiction!

Trap Door

  1. With engine off, remove air cleaner and check position of trap door. It should be closed.
  2. Remove vacuum hose from intake manifold vacuum source and apply an external vacuum source of approximately 2-4 in. Hg. Trap door should open.
  3. If door does not open, apply vacuum directly to vacuum motor. If door does not open, check for binding and adjust as necessary. If door swings freely, replace vacuum motor.
  4. If door opens during step  3), check vacuum hose for blockage, cracks or leaks. Correct as necessary and retest as specified in step  2).
  5. If hoses are not defective, remove reverse delay valve, join vacuum hose and retest from step  2). If door opens, replace reverse delay valve.
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