Pressurizing the Fuel Tank System, Check

Pressurizing The Fuel Tank System, Check

Removal

Safety precautions

CAUTION: Never leave the car unattended with its system pressurized. Always reset the system pressure after carrying out the measurements. line pressure in the fuel injection system is between 15 and 20 kPa.

Always use a exhaust gas management system when opening the fuel injection system.

Preparations







- Before measurements are carried out check that the pressure valve in the fuel tank filler cap functions correctly
- See the test for the fuel tank filler cap Fuel cap, test equipment
- Use the following test values:
- Low pressure 5 - 10 kPa.
- Low pressure 15 - 20 kPa

- Check the evaporative emission system (EVAP) valve (when the pressure gauge is connected).

Connecting pressure gauge 999 5230







- Open the hood. Remove the hose connector (A) leading to the rear section of the car from the evaporative emission system (EVAP) valve.
- Connect pressure gauge 999 5230 to the pipe. Use the connection section for special tool 999 5757.

Checking the evaporative emission system (EVAP) valve







- Disconnect the connector terminal. Install vacuum pump 999 5843 on the terminal(B) and pump until there is a vacuum. The vacuum must be maintained.
- If the vacuum drops or there is no vacuum: replace the evaporative emission system (EVAP) valve.
- If the vacuum is maintained: connect 12 volts and ground to the evaporative emission system (EVAP) valve electrical terminal, the vacuum should not remain and pumping should be made easier.
- Ensure that the air can flow freely via the other terminal (A). Reconnect the terminals earlier removed.

Connecting the compressed air system to the leak diagnostic pump (LDP)







- Raise the car
- Clean the terminals on the leak diagnostic pump (LDP)
- Disconnect the hose (A) from the reverse of the leak diagnostic pump (LDP)
- Plug the terminal (B) on the leak diagnostic pump (LDP) using a hose and plug
- Slacken off the terminal at the bottom of the pump cover, this leads upwards in the wheel arch
- Connect pressure regulator 999 5646 to the leak diagnostic pump (LDP) terminal Use a connection section from 999 5757.

Pressurize the system to check







- Connect the compressed air system in the workshop to the pressurized system
- Set a pressure of maximum 20 kPa
- Turn the stop cock so that the compressed air enters the system
- Pressurize the system holding the drain cock open for 5 minutes.
- Check the pressure on the manometer 999 5230 at the Evaporative emission system (EVAP) valve. Close the cock when the pressure exceeds 25 kPa.

System check







- Disconnect the compressed air connections from the leak diagnostic pump (LDP). Listen for or feel if the disconnected hose (A), (the removed hose), is leaking.
- Check if there are any other leaks. In the event of any leakage, replace the entire leak diagnostic pump (LDP) as the leakage is internal.

Check the pressure drop in the system







- The built-up pressure drops to a value between 17 and 20 kPa.

CAUTION: The pressure must remain at the minimum level for at least 30 minutes.

- If the pressure drops further the leakage must be located and remedied. If the system cannot be pressurized there is a large leak which must be rectified.

HINT: Tip: when the fuel injection system has reached a certain pressure 20 kPa the leak diagnostic pump (LDP) functions as shut off device for the evaporative emission (EVAP) system. This takes place when the compressed air supply is switched off.

- If the pressure in the system is higher, it will drop to between 17 and 20 kPa and then remain at that level.

Installation

Installing the components on the leak diagnostic pump (LDP)







- Remove the pressure gauge and the governor
- Remove the plug (A) from the leak diagnostic pump (LDP) and reconnect the existing hose. Check that the hose (A) is installed far enough in on the terminal mounting
- Install a new hose clamp and align the hose (A) on the terminal to the filter on the leak diagnostic pump (LDP) housing
- Secure the hose using special tool 951 2619.

Installing components







- Remove the pressure gauge from the hose
- Re-install the hose on the evaporative emission system (EVAP) valve. Secure the hose clamp in the correct position.