DESCRIPTION
The purpose of the Evaporative Control System is to prevent the emission of gasoline vapors from the fuel tank into the atmosphere.
When fuel evaporates in the fuel tank and fuel bowl (carburetor models), the vapors are temporarily held in the charcoal canister until they can be drawn into the intake manifold when the engine is running.
CANISTER PURGE SOLENOID
The purge solenoid is controlled by the Single Module Engine Controller (SMEC). When engine temperature is less than 145°F (61°C), the SMEC grounds the purge solenoid, energizing it. This prevents vacuum from reaching the charcoal canister valve.
When engine temperature reaches 145°F (61°C), the SMEC de-energizes the solenoid by turning the ground off. Once this happens, vacuum will flow to canister purge valve and purge the fuel vapors.
CHARCOAL CANISTER
A sealed, maintenance free, charcoal canister is used on all models. Fuel vapors from the fuel tank, throttle body or carburetor are temporarily stored in the canister until they can be drawn into the intake manifold.
On 5.2L, 2-Bbl. engines, canister is purged by intake manifold vacuum through a vacuum connection on the carburetor.
PRESSURE-VACUUM FILLER CAP
Fuel tank is sealed with a pressure-vacuum relief filler cap. Relief valves in fuel tank filler cap operate only to prevent excessive pressure or vacuum in fuel tank. Proper replacement cap must be used to replace original cap.
ROLLOVER/VAPOR SEPARATOR
All models are equipped with a rollover/vapor separator valve to prevent fuel leakage if vehicle is accidentally rolled over. This valve is located on top of fuel tank.
TESTING
Note. Testing information not available.
MAINTENANCE
Charcoal canister control device can be checked by disconnecting the 3/16" vacuum hose to canister and connecting an auxiliary vacuum source in its place. Delay device must hold 10 in. Hg. 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 necessary. Use only fuel resistant hose.