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Home >> GMC >> 1987 >> Forward Control 5.7 M, Automatic, 400/M40 >> Repair and Diagnosis >> Engine Performance >> System >> Air Injection System - Vehicles Over 8500 GVW >> Component Testing >> Air Control Valve
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Air Control Valve

  1. Ensure that air pump is working properly. Disconnect solenoid connector at valve. Turn ignition "ON". Check for 12 volts at connector. If no voltage is present, refer to diagnostic charts. See Figure , Figure and Figure . Start engine. Air should flow to air cleaner or silencer. Connect solenoid connector. Air should flow to exhaust ports.
  2. Check for manifold vacuum signal at valve with engine idling. Vacuum should be 10" Hg (34 kPa). During deceleration and high vacuum signal conditions, air should flow to air cleaner and silencer. If airflow does not conform to specifications, replace air control valve.
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