Fuel Evaporation System: Maintenance
Charcoal canister control device can be checked by disconnecting the top vacuum hose to canister and connecting an auxiliary vacuum source in its place. Delay device must hold 10 inches of vacuum. If not, replace canister.
Generally, replacement is only required if vehicle is frequently driven in dusty areas or filter is dirty or clogged. All hoses should be inspected periodically and replaced if cracked or leaking.