Fuel Delivery and Air Induction: Testing and Inspection

Fuel System, Checking for Leaks

Special tools, testers and auxiliary items required

• Fuel system tester (smoke tester) (KLI 9210)

• Hose adapter (KLI 9210/55-1)

• Vehicle diagnostic tester

• Hose clamps up to 25 mm diameter (3094)

Test conditions:

• Perform Guided Fault Finding using the Vehicle Diagnosis Tester.

• The leak detection pump (V144) detected a leak.

Perform the following:

Evaporative Emissions Tester (KLI 9210) preparation:

• Depending on the version, the appearance of the evaporative emissions tester (KLI 9210) may vary.

- Check the evaporative emissions tester (KLI 9210) to make sure there is enough fluid in the smoke generator.

- Set the valve - D - to "Hold".

- Open the nitrogen bottle - H -.

- Connect the measuring hose - G - to the self-test connection - B -.

- Set the valve - D - to "Test".

- Using the pressure reducer - J -, adjust the pressure to 25 mbar (10 in. H2O).

- Set the valve - D - to "Hold".

• The pressure must now be maintained for a minimum of 2 minutes.

If the pressure is not maintained, check the tester.

Fuel System, Checking for Leaks:

- Connect the adapter hose (KLI 9210/55-1) to the bleed line - A - as illustrated.

- Connect the measuring hose - G - on the evaporative emissions tester (KLI 9210) to the adapter hose (KLI9210/55-1).

- Connect the Vehicle Diagnosis Tester to the vehicle.

- Switch the ignition on.

• The engine may be not running.

- Select the type of operation for Guided Functions on the Vehicle Diagnosis Tester.

- Select the "Check tank ventilation system for leaks".

- Start the test.

- Watch the pressure gauge on the evaporative emissions tester (KLI 9210).

• The leak detection pump (V144) must pump the fuel system pressure up to at least 18 mbar (7 in. H2O).

The minimum pressure is not reached and the pressure reached decreases immediately:

There is a large leak in the fuel system.

- Turn off the ignition.

- Perform "large lead in the fuel system" check. Refer to => [ Large leak test in fuel system ].

The minimum pressure is not reached:

- Turn off the ignition.

• The valve in the leak detection pump (V144) is now closed. The pressure is held.

- Set the valve - D - to "Test". Increase the current pressure to 25 mbar (10 in. H2O).

- Repeat the pressure test. Set the valve - D - to "Test" again.

- Watch the pressure gauge - C - and the flow meter - E -.

If the flow quantity decreases and pressure increases to 25 mbar (10 in. H2O), then the fuel system is full.

- After the pressure has stabilized, set the valve - D - to "Hold".

If pressure no longer drops now:

- Replace the evaporative emission canister purge regulator valve (N80).

If pressure still drops:

- Remove right rear wheel housing liner => Body Exterior 66 Wheel housing liner.

- Disconnect the line - arrow - from the leak detection pump (V144) and seal the opening tight.

- Set the valve - D - to "Test".

- Watch the pressure gauge - C - and the flow meter - E -.

If the flow quantity decreases and pressure increases to 25 mbar (10 in. H2O), then the fuel system is full.

• Depending on the level in the fuel tank, this procedure may take up to 3 minutes.

- After the pressure has stabilized, set the valve - D - to "Hold".

• After 5 minutes the pressure must not drop below 20 mbar (8 in. H2O).

- If the pressure stops falling, replace the leak detection pump (V144).

If pressure still drops:

- Set the valve - D - to "Test".

- While fuel system is being filled, press smoke generator button - I - for approximately one minute.

The fuel system is now under pressure and filled with smoke.

- Check all fuel system lines and hoses for escaping smoke. Also check the fuel cap.

• Locations => [ EVAP System Overview ] Service and Repair

• Shine a strong light on the components and hoses. The smoke will be more visible.

• To check for leaks at accessible locations, also use ultrasonic measuring device or commercially available leak detection spray.

• Depending on how long fault finding lasts, the smoke generator button may need to be pressed again. This ensures there is enough smoke present in the fuel system.

• Remove the cover - 1 - to check the fuel delivery unit flange.

- Replace any leaking hoses or components.

After completing the work, perform the "Check tank ventilation system for leaks" guided function with the vehicle diagnosis, testing and information system.

Large leak test in fuel system

Test conditions:

• Evaporative Emissions Tester (KLI 9210) with Adapter Hose (KLI 9210/55-1) connected to vehicle. Refer to => [ Fuel System, Checking for Leaks ] Testing and Inspection.

Perform the following:

- Connect the evaporative emissions tester (KLI 9210) to the vehicle battery.

- Remove right rear wheel housing liner => Body Exterior 66 Wheel housing liner.

- Disconnect the line - arrow - from the leak detection pump (V144) and seal the opening in the pump tight.

- Set the valve - D - to "Test".

- While fuel system is being filled, press smoke generator button - I - for approximately one minute.

The fuel system is now under pressure and filled with smoke.

- Check all fuel system lines and hoses for escaping smoke. Also check the fuel cap.

• Locations => [ EVAP System Overview ] Service and Repair

• Shine a strong light on the components and hoses. The smoke will be more visible.

• To check for leaks at accessible locations, also use ultrasonic measuring device or commercially available leak detection spray.

• Depending on how long fault finding lasts, the smoke generator button may need to be pressed again. This ensures there is enough smoke present in the fuel system.

• Remove the cover - 1 - to check the fuel delivery unit flange.