Operating principle
The ECS system is used to reduce the release of hydrocarbon compounds from the fuel tank into the atmosphere.
The principle of the system
1 - fuel tank; 2 - one-way control fuel valve; 3 - to TVV (only 3.0 l); 4 - throttle valve; 5 - inlet pipeline; 6 - carbon adsorber
Key system components include a charcoal canister, purge control valve, hermetically sealed fuel tank and, on 3.0L models, a thermal vacuum valve (TVV).
Purge control valve and charcoal canister location on 4.2L models
When the engine is not running, fuel vapor gradually fills all the fuel-free space in the gas tank. Since the tank is equipped with a sealed lid, the vapor pressure rises and they are forced into the carbon adsorber, where they accumulate. The one-way check valve prevents liquid fuel from entering the adsorber.
When the engine is started, a small amount of vapor enters the intake manifold through the constant scavenge orifice and is burned as part of the air/fuel mixture. With an increase in engine speed, the main throttle purge opening of the adsorber opens, from which a larger volume of fumes accumulated during the parking period is removed.
On 3.0L models, a special thermal vacuum valve is used to shut off the main purge throttle at low engine temperatures (TVV).
Service
Note. Maintenance of the system should be carried out regularly, with particular attention to the points listed below.
1. Check the patency and external condition of all hoses in the system.
2. Check the condition of the sealing gasket of the fuel filler cap (see accompanying illustration). Check that the pressure relief valve is working properly.
3. Check the function of the charcoal adsorber and one-way control valve.
Checking the carbon adsorber
1. Inspect the canister for signs of damage or leaks. Replace if necessary.
2. Mark and disconnect from an adsorber hoses.
3. Blow into the upper purge control hose fitting. Air must not pass.
4. Blow into the bottom purge hose fitting. Air must pass freely.
5. Blow into the inlet hose fitting. Air must also be blown.
6. If necessary, replace the adsorber.
Checking the one-way control valve
1. Remove the valve from the fuel tank (see accompanying illustration).
2. Blow into the valve fitting facing the fuel tank. Air must not pass.
3. Blow into the valve fitting located on the side of the charcoal adsorber. The air passage must be free.
4. Replace the valve if necessary.