Gasoline Engines Only
Check the evaporation control system every 12,000 miles (15,000 miles, 1980 and later). Check the fuel and vapor lines for proper connections and correct routing as well as condition. Replace damaged or deteriorated parts as necessary. Remove and check the operation of the check valve on pre-1975 models in the following manner.
- With all the hoses disconnected from the valve, apply air pressure to the fuel tank side of the valve. The air should flow through the valve and exit the crankcase side of the valve. If the valve does not behave in the above manner, replace.
- Apply air pressure to the crankcase side valve. Air should not pass to either of the two outlets.
- When air pressure is applied to the carburetor side of the valve, the air should pass through to exit out the fuel tank and/or the crankcase side of the valve.
On 1975 and later models, the flow guide valve is replaced with a carbon filled storage canister which stores fuel vapors until the engine is started and the vapors are drawn into the combustion chambers and burned.
On those vehicles built through 1983, you should check the operation of the carbon canister purge valve. To do this, 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 an air filter in the bottom of the canister. On models built in years up to and including 1982, the filter element should be checked every two years or 30,000 miles; more frequently if the car is operated in dusty areas. Replace the filter by pulling it out of the bottom of the canister and installing a new one.