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Normally Closed Valve

  1. With engine at normal operating temperature, parking brake applied and transmission in Park or Neutral, disconnect air supply line at valve outlet. Remove vacuum line and ensure that a vacuum signal is present at nipple.
  2. Remove any delay valves or restrictors in line. Vacuum must be present at nipple before proceeding. With engine speed at 1500 RPM and vacuum line connected to nipple, air pump supply air should be heard and felt at outlet.
  3. With engine at 1500 RPM, disconnect vacuum line. Air at outlet should be significantly decreased or shut-off. Air pump supply air should be heard or felt at silencer ports.
  4. If valve fails any test and air pump is operating properly, replace valve. Reconnect all vacuum lines.
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