Pulse Air Injection: Testing

Start the engine. Disconnect upper wire from the thermocontact and alternately put it in contact with lower wire on thermocontact.
The pulse air valve should hum slightly and diaphragm movement should be seen through the upper section. If so, system is okay. Reconnect wire.
If not, check operation of the electrovalve, electrical and vacuum hose connections. If okay, replace electrovalve.