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Normally Open Valve With Vacuum Vent

  1. With engine at normal operating temperature, parking brake applied and transmission in "P" or "N," disconnect air supply line at valve outlet. Disconnect all vacuum lines from vacuum nipple and vent.
  2. With engine at 1500 RPM, air pump supply should be heard and felt at outlet. Connect a vacuum line from vacuum nipple to one of the vacuum fittings on intake manifold. With vacuum vent open to atmosphere and engine at 1500 RPM, no air should be felt at outlet and all air should be bypassed through silencer ports.
  3. Using the same direct line to an intake manifold vacuum source, cap vacuum vent. Accelerate engine to 2000 RPM and suddenly release throttle. A momentary interruption of air pump supply air should be felt at outlet.
  4. If valve fails any test, and air pump is operating okay, replace valve. Reconnect all vacuum lines.
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