DESCRIPTION
The purpose of the Evaporation Control System is to prevent gasoline vapors (hydrocarbons) from the fuel tank, carburetor and throttle body, from entering the atmosphere.
When fuel evaporates in the fuel tank, fuel bowl (carburetor models) or throttle body (EFI and turbo models), the vapors pass through vent hoses to a charcoal canister. The EFI system, having only 2 hoses to the throttle body, uses an in-line purge solenoid (opens when engine is running) to extract vapors from the canister.
The vapors are stored in the charcoal canister until they are drawn into the intake manifold after the engine begins to run. (Scheme 10)and (Scheme 11).
CARBURETOR FUEL BOWL
Fuel bowls on all carburetors are vented internally. Because of internal venting of fuel bowl, some models do not require venting to canister. In this case, bowl vent port on canister will be capped. Most carburetors are also externally vented to charcoal canister.
FUEL BOWL VENT SOLENOID VALVE
Fuel bowl solenoid valve, located on some carburetors, controls movement of carburetor waste vapors. When ignition is turned "ON", solenoid valve closes passage to charcoal canister and opens passage to intake manifold. When ignition is turned "OFF", solenoid valve opens passage to charcoal canister and closes passage to intake manifold.
Except 5.2L
Fuel bowl vent valve is connected between carburetor, charcoal canister and air pump. When engine is not running, fuel bowl vapors can pass to canister. When engine is running, air pump pressure closes valve between fuel bowl and canister.
CHARCOAL CANISTER
A sealed canister is used on all models. Fuel vapors from fuel tank are stored in activated charcoal while engine is not operating. When engine is operating, vapor is purged from canister into engine where it is burned with air/fuel mixture. When engine is operating, fuel evaporating from carburetor or throttle body passes to the canister. Canister is located in the wheelwell area.
On 5.2L engines, canister is purged by intake manifold vacuum through a vacuum connection on the carburetor.
DAMPING CANISTER
On 2.6L engines, a damping canister is used as a purge control device. It does not store vapor and is separated from them by the closed purge control valve. It is connected to the purge line in series with the primary canister and intake manifold. The damping canister cushions the effect of a sudden release of rich fuel vapors (when the purge control valve is opened) by temporarily holding vapors before they are gradually phased into manifold.
FUEL TANK FILLER CAP
Relief valves in fuel tank filler cap operate to prevent excessive pressure or vacuum in fuel tank. Proper replacement cap must be used if original cap is lost or damaged.
| CAUTION | Remove fuel tank filler cap prior to removing or repairing fuel lines. |
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 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.
