Air Pump Test

1. Accelerate engine to about 1500 RPM and observe air flow from hose(s). If air flow increases as engine is accelerated, the pump is operating satisfactorily. If not, proceed as follows:
2. Check for proper drive belt tension.
3. Check for leaky pressure relief valve. Air may be heard leaking with the pump running. The air pump is not completely noiseless. Under normal conditions noise rises in pitch as engine speed increases. To determine if excessive noise is the fault of the system, operate the engine with the pump drive belt removed. If excessive noise does not exist with the belt removed, proceed to next step.
4. Check for proper installation of the relief valve silencer if so equipped.
5. Check for seized air pump.
6. Check hoses, tubes, air manifolds and all connections for leaks and proper routing.
7. Check carburetor air cleaner for proper installation.
8. Check air pump for proper mounting.
9. If none of the above conditions exists and the air pump has excessive noise, replace the pump.

Air Switching Valve (Combination Switch/Relief Valve) Test
Apply vacuum to the valve. Ensure air injection is applied upstream. If there is no vacuum upstream, replace valve.