Air Pump Test

With engine at normal operating temperature and all hose connections tight, check air injection pump belt tension and adjust if necessary. Disconnect air supply hose at check valve and connect suitable air pump test gauge (ST19870000). Position gauge outlet so air will be discharged harmlessly. With engine running at 1500 RPM, air pump output should exceed 0.63 in (16 mm) Hg. If pressure is not to specifications, recheck all hoses and belt tension, check air cleaner element and recheck output. If still not to specifications, close hole of test gauge with finger. If a leaking sound is heard at relief valve, valve is bad and should be repaired or replaced. If pump still fails test, pump is defective and should be repaired or replaced.