Charcoal Canister
- Connect tachometer and warm engine to normal operating temperature. Remove fuel filler cap. Remove canister purge air hose from canister and connect vacuum gauge to purge air port. See Fig 1 . Run engine at 3500 RPM. If vacuum appears on gauge within 1 minute, remove gauge and proceed to step 5). If not, stop engine, disconnect vacuum gauge, and reinstall fuel filler cap. Check charcoal canister for damage or defects. If defective, replace canister.
- If canister is OK but there is no vacuum at 3500 RPM after 1 minute, disconnect hoses from purge control valve port and purge port on canister. Connect vacuum pump to canister purge port (lower port) and draw vacuum. Vacuum should remain steady. If vacuum drops, replace canister and retest.
- If vacuum holds steady, reconnect purge control valve hose to canister port and start engine. Check that purge port vacuum drops to zero. If purge port vacuum does not drop to zero, remove hose from purge control valve port on canister and check for vacuum at the hose. If there is vacuum at hose, replace canister and retest. If there is no vacuum at hose, recheck thermovalve operation. (See step 3) in previous thermovalve test).
- If purge port vacuum drops to zero, connect purge hose to vacuum gauge and run engine at 3500 RPM. If there is vacuum at hose, replace canister and retest. If there is no vacuum at purge hose, check hose for leaks and obstructions, and check carburetor port for blockage. Repair and retest.
- Connect vacuum pump to tank port on canister and try to draw vacuum. There should be no vacuum. If there is vacuum, replace canister and retest.