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Home >> GMC >> 1987 >> Forward Control 5.7 M, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Air Injection System - Vehicles Over 8500 GVW >> Component Testing >> Air Pump
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Air Pump

  1. Air pump is permanently lubricated and requires no periodic maintenance. Accelerate engine and observe air flow from hose(s). If air flow increases as engine is accelerated, pump is operating satisfactorily.
  2. If air flow does not increase or is not present, inspect for correct drive belt tension or leaking pressure relief valve. Air may be heard from leaking relief valve with pump running.