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Normally Closed Valve

  1. With engine at normal operating temperature, parking brake applied, and transmission in Park or Neutral, disconnect hoses from ports "A" and "B". See Figure . Disconnect and plug line to port "D". With engine speed at 1500 RPM, air should flow from by-pass vents.
  2. Reconnect line to port "D". Disconnect and plug line to port "S". Ensure vacuum is present in line to port "D". With engine speed at 1500 RPM, air should flow from port "B", and no air should flow from port "A".
  3. Apply 8-10 in. Hg vacuum to port "S". With engine speed at 1500 RPM, air should flow from port "A". If valve has a vacuum bleed, some lesser amount of air will flow from port "A" or "B", and main discharge will change when vacuum is applied to port "S".
  4. If valve fails any test, it must be replaced. Reconnect all vacuum hoses.
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