Air Pump Troubles

Replace pump if it develops excessive noise and does not rotate freely. Replace pump if air pressure relief valve is defective or leaks. (Relief valve is a press fit in the pump housing). Relief valve should open at an engine speed of 1, 700 to 2, 000 RPM. To Check: move gear shift lever to neutral, remove relief valve hose connection and attach tachometer. Holding your hand at valves discharge port, increase engine speed until valve opens. If the valve opens at a lower engine speed either the "pressure setting plug" of the valve assembly is improperly set (if so insert new plug) or the valve was damaged. If the relief valve should not open, or only at a higher speed, it is defective and the pump has to be exchanged.