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Home >> GMC >> 1989 >> Forward Control 4.8 T, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Air Injection System >> Component Testing >> Diverter Valve

Diverter Valve

Ensure air pump operates properly. Start engine. Air should enter exhaust ports. Check for manifold vacuum signal at valve with engine idling. Vacuum should be 10 in. Hg (34 kPa). During decel and high vacuum signal, air should go to air cleaner and silencer. Replace valve if any conditions are incorrect.