General information
1. The evaporative emission system absorbs fuel vapors so that they do not enter the atmosphere, and at the right moment when the engine is running, sends these vapors to the engine intake tract, where they mix with the working mixture and burn in the cylinders.
2. The main element of the vapor recovery system is the carbon filter (absorber), filled with activated carbon like a gas mask box. The steam control system is different for different models, but the principle of its operation is almost the same.
Note. Below is a description of a typical vapor recovery system to help you understand how the system works on your vehicle. The description below is not a description of the system installed specifically on your car. This is a description of a system typical of vehicles equipped with fuel injection. Although most of the devices listed here are on your vehicle, however, some devices may be missing, and some devices not listed here may be present. Specify the composition of the system on the plate under the hood with information on emission control systems (VECI) (pic 1.5).
3. The fuel tank filler cap is equipped with a safety valve. which, in the event of a malfunction in the vapor recovery system, releases fuel vapors into the atmosphere.
4. There is another valve in the fuel tank through which fuel vapors are directed from the neck to the carbon filter when filling the tank.
5. Fuel vapors are directed through valves to a carbon filter located in the engine compartment and filled with activated carbon, which absorbs vapors and stores them.
6. When the engine warms up to a preset temperature, the filter purge control solenoid valve is activated. Vacuum is applied through the solenoid valve from the intake manifold to the diaphragm of the purge valve, which communicates the carbon filter with the intake manifold. Under the action of rarefaction, fuel vapors are sucked from the carbon filter into the manifold.
7. A pressure sensor is installed in the fuel tank, which monitors the vapor pressure in the tank with the engine running and not running.
Examination
Note. A complete check of the evaporative emission system is beyond the capabilities of the car owner. Usually the system is very reliable and does not require intervention throughout the entire life cycle of the vehicle. If a system failure does occur, then, as a rule, the hoses and the carbon filter are most likely to blame.
8. First of all, check the hoses. The most common cause of fuel vapor management system failure is a torn or loose hose. To check the correct routing and fastening of the hoses, see the plate with the diagram of the vacuum hoses under the hood (see fig. 1.5). Replace or fix hoses.
9. Disconnect the vacuum hose from the carbon filter and attach a vacuum gauge to the hose. When the engine is idling and the coolant temperature is below 65°C, there should be no vacuum in the hose. If there is a vacuum in the hose, then the vacuum control solenoid valve may be faulty (see point 14). If there is no vacuum in the hose, raise the engine speed to 3000 rpm and let it warm up until the fan turns on. A vacuum should appear in the hose. If there is no vacuum, check the solenoid valve (see item 14).
10. Disconnect the vacuum hose from the valve located next to the carbon filter and connect a vacuum pump to the hose. The vacuum pump must be connected to the valve. With the ignition on (the engine is not running! create a vacuum with the pump and make sure that the valve holds the vacuum securely. If the valve is leaking, replace it.
11. With the ignition on and the engine off, disconnect the electrical connector from the vacuum control solenoid valve. Battery voltage must be present at the connector pins. If there is no voltage, check the power target, find and repair the problem.
12. Warm up the engine to normal operating temperature (cooling fan should turn on). Check the passage of vacuum from the intake manifold through the solenoid valve. If there is no vacuum, disconnect the valve electrical connector and check if there is vacuum now. If there is still no vacuum. check if the system hoses are routed correctly. If a vacuum appears after disconnecting the connector, check the circuit between the connector and the BEU for a short circuit.
13. Check the carbon filter for leaks. Remove the charcoal filter and plug all of its openings. Connect a vacuum pump to the charcoal filter shut-off valve, create a vacuum and check that there is no air suction. If the carbon filter is defective, replace it.
Replacement
Carbon filter
14. Disconnect all hoses from the carbon filter, unscrew the filter mounting bolts and remove it from the car. Before disconnecting the hoses, mark them so as not to be mixed up during installation.
15. Installation is carried out in reverse order.
Solenoid valve
16. Disconnect the vacuum hoses from the solenoid valve.
17. Turn away a bolt of fastening of the valve and remove the valve from the car.
18. Installation is carried out in the reverse order.