See Figures 1 through 5
Check the evaporation control system, if so equipped, every 15,000 miles (24,000 km) or every 12 months. Check the fuel and vapor lines/hoses for proper connections, correct routing, and condition. Replace damaged or deteriorated parts as necessary.
To check the operation of the carbon canister purge control valve, disconnect the rubber hose between the canister control valve and the T-fitting at the T-fitting. Apply vacuum to the hose leading to the control valve. The vacuum condition should be maintained indefinitely. If the control valve leaks, remove the top cover of the valve and check for a dislocated or cracked diaphragm. If the diaphragm is damaged, a repair kit containing a new diaphragm, retainer, and spring is available and should be installed.
The carbon canister has a replaceable air filter in the bottom of the canister. The filter element should be checked once a year or every 15,000 miles (24,000 km); more frequently if the truck is operated in dusty areas. Replace the filter by pulling it out of the bottom of the canister and installing a new one.