DESCRIPTION
Evaporation control system prevents fuel tank and carburetor gasoline vapors from escaping into the atmosphere. The systems are dual canister types for "B","D","W" and 2.6L Federal High Altitude "H" or "K" models. All other "H" and "K" models have single canister type systems with damping canisters on 2.6L models.
Typical Dual Canister Mounting ("D" & "W" Models) Canisters are mounted on right front fender. Scheme 40
OPERATION
When fuel evaporates in carburetor float chamber or fuel tank, vapors pass through vent hoses or tubes to the charcoal canister.
Fuel vapors are held on the activated charcoal surface until they are drawn into the intake manifold (when the engine is running). Vacuum port in carburetor base controls vapor flow to engine.
Typical Evaporation Control System Hose Routing ("D" & "W" Models). Scheme 41
On dual canister systems, fuel vapors from primary canister are purged through carburetor port. When distributor vacuum signal activates purge switch, vapors from secondary canister are purged through PCV hose to carburetor.
On single canister systems, all fuel vapors are stored in one canister and are purged into intake manifold when engine is started. Damping canister is used on "H" and "K" models with 2.6L engines. It cushions sudden releases of fuel vapors when purge control valve opens. Fuel vapors are held in canister and gradually released into intake manifold.
Typical Vapor Hose Routing for Dual Canister ("B" Models). Scheme 42
TESTING
Note. Testing information not available.
MAINTENANCE
There is no service required on the fuel evaporation control system, except replacement of the filter element in the charcoal canister. Replace filters every 18,000 miles on Heavy Duty Emission models (over 8500 lbs. GVW). On all other models replace filter every 30,000 miles.