System Testing

Check condition of all hoses and tubes. On Federal models, disconnect air suction hose from air cleaner. Start engine. With engine idling, check that air is drawn into inlet pipe.
On Calif. models, disconnect vacuum hose from AS valve and plug hose end. Remove air cleaner cap. Start engine. Reconnect vacuum hose to AS valve and check that bubbling noise is heard from AS valve inlet within 2-6 seconds. Reinstall the air cleaner cap.
To check AS valve on Federal models, blow and suck on pipe. Check that no air passes when you blow hard, but air passes when sucked. On Calif. models, remove air filter and AS valve from air cleaner.
Check and clean filter. Blow air into pipes and apply vacuum to diaphragm. Check that air flows from filter side to outlet pipe. Check that air does not flow from outlet pipe to filter side.
Release vacuum. Check that hardly any air flows from filter side to outlet pipe. Reinstall AS valve. Check VTV by blowing air into each side. Check that air flows without resistance from side B to side A. Check that air flows with difficulty from side A to side B. If problem is found, replace the VTV.

Fig 1: Air Suction System (California Models Shown)