General information
1. The fuel vapor recovery system absorbs fuel vapors so that they do not enter the atmosphere, and at the appropriate moment, when the engine is running, sends these vapors into the engine intake tract, where they mix with the working mixture and burn in the cylinders.
2. The main element of the vapor collection system is a carbon filter (absorber) filled with activated carbon, similar to a gas mask box. The steam control system varies for different models, but the operating principle is almost the same.
Note: Below is a description of a typical evaporative emission system to help you understand how the system works in your vehicle. The description below does not describe the system installed specifically on your vehicle. This is a description of a system typical for vehicles equipped with fuel injection. Although most of the devices listed here are present in your vehicle, some devices may be missing, while others not listed here may be present. To find out the system composition, refer to the Emission Control Information (VECI) plate under the hood (fig. 1.5).
3. The fuel tank filler cap is equipped with a safety valve. which, in the event of a failure of 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 filler neck to the carbon filter when filling the tank.
5. Fuel vapors are directed through valves into a carbon filter located in the engine compartment and filled with activated carbon, which absorbs the vapors and stores them.
6. When the engine warms up to a preset temperature, the filter purge control solenoid valve is activated. Through the electromagnetic valve, a vacuum is supplied from the intake manifold under the diaphragm of the purge valve, which connects the carbon filter to the intake manifold. Under the action of vacuum, 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 when the engine is running and not running.
Examination
Note: A complete inspection of the fuel vapor removal system is beyond the capabilities of the vehicle owner. The system is generally very reliable and requires no intervention throughout the vehicle's life cycle. If a system failure does occur, the hoses and carbon filter are usually the culprit.
8. First of all, check the hoses. The most common cause of evaporative emission control system failure is a broken or loose hose. To check that the hoses are correctly routed and secured, see. a plate with a diagram of the vacuum hoses under the hood (see figure 1.5). Replace or secure the 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, the vacuum control solenoid valve may be faulty (see item 14). If there is no vacuum in the hose, increase 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 serviceability of 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. When the ignition is turned on (the engine does not work! 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 not running, disconnect the electrical connector from the vacuum control solenoid valve. There should be battery voltage at the connector contacts. If there is no voltage, check the power supply target, find and fix the problem.
12. Warm up the engine to normal operating temperature (the cooling system fan should turn on). Check for vacuum flow from the intake manifold through the solenoid valve. If there is no vacuum, disconnect the valve electrical connector and check to see if there is vacuum now. If there is still no vacuum. check that the system hoses are routed correctly. If vacuum appears after disconnecting the connector, check the circuit between the connector and the ECU for a short circuit.
13. Check the carbon filter for leaks. Remove the carbon filter and plug all its holes. Attach a vacuum pump to the carbon filter shut-off valve, create a vacuum and make sure there is no air leak. If the carbon filter is faulty, replace it.
Replacement
Carbon filter
14. Disconnect all hoses from the carbon filter, unscrew the filter mounting bolts and remove it from the vehicle. Before disconnecting the hoses, mark them to avoid confusion during installation.
15. Installation is carried out in reverse order.
Solenoid valve
16. Disconnect the vacuum hoses from the solenoid valve.
17. Loosen the valve mounting bolt and remove the valve from the vehicle.
18. Installation is carried out in reverse order.