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Fuel System, Checking for Leaks






Fuel System, Checking for Leaks

Special tools, testers and auxiliary items required

Hose Clamps Up to 25 mm Dia. (3094)

Vehicle Diagnostic Tester

Evaporative Emission Tester (KLI 9210)

Adapter Hose (KLI 9210/55-1)

Test Conditions:

The "Guide Fault Finding" was performed using the vehicle diagnostic tester.

A leak in the leak detection pump (V144) was detected.

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 determine whether there is enough fluid in the smoke generator.

- Set valve - D - to "Hold".






- Open the nitrogen bottle - H -.

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

- Set valve - D - to "Test".

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

- Set 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.

Test Sequence:

- Read the safety precautions before starting. Refer to => [ Safety Precautions ] Fuel Supply.

- Pay attention to the rules of cleanliness. Refer to => [ Clean Working Conditions ] Fuel Supply.

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






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






- Connect the vehicle diagnostic tester - 1 - as follows:






- Connect the diagnostic cable - 2 - to the Data Link Connector (DLC) in the drivers foot well.

- Start the engine and run at idle speed.

- Select Guided Functions on the vehicle diagnostic tester.

- Select Check tank ventilation system for leaks "guided function".

- Start the test.

- While the test runs, observe the pressure gauge on the evaporative emissions tester (KLI 9210) :

The Leak Detection Pump (LDP) must pump the fuel system up to a min. 18 mbar (7 in. Inflate H2O (18 mbar).

The minimum pressure is not reached, but the pressure reached does not decrease:

- Turn off the ignition.

- Perform a pressure retention test.

If no decrease in pressure is observed:

- Check the vacuum supply for the LDP. Refer to => [ Vacuum Supply, Checking ] Leak Detection Pump (V144) Vacuum Supply, Checking.

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

- Using a hose clamp up to 25 mm dia. (3094) - arrow -, clamp off the hose to the EVAP canister purge regulator valve 1 (N80).






- Repeat the test.

If the minimum pressure is not reached:

- Replace the EVAP canister purge regulator valve 1.

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

- There is a leak in the fuel system, perform the "fuel system leak test". Refer to => [ Fuel System Leak Test ] Fuel System Leak Test.

If the minimum value is obtained:

- Turn off the ignition.

The valve in the LDP is now closed and the pressure is maintained.

- Observe the pressure gauge:

If the pressure does not drop:

- Perform a pressure retention test to locate any possible pinhole leaks.

If the pressure drops:

- Using a hose clamp up to 25 mm dia. (3094) - arrow -, clamp off the hose to the EVAP canister purge regulator valve 1.






If the pressure no longer drops now:

- Replace the EVAP canister purge regulator valve 1.

If the pressure still drops:

- There is a leak in the fuel system, perform the "fuel system leak test". Refer to => [ Fuel System Leak Test ] Fuel System Leak Test.

Pressure Retention Test






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

- Observe the pressure gauge - C - and flow meter - E -. If the flow quantity decreases and pressure increases to 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 valve - D - to "Hold":

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

If the pressure is not maintained for 5 minutes, the leak should be localized as follows:

- First, check the EVAP canister purge regulator valve 1 for leaks. Using a hose clamp up to 25 mm dia. (3094) - arrow -, clamp off the hose to the EVAP canister purge regulator valve 1.






- Repeat the pressure test by resetting valve - D - to "Test".






- Observe the pressure gauge - C - and flow meter - E -:

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

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

If the pressure no longer drops now:

- Replace the EVAP canister purge regulator valve 1.

If the pressure still drops:

- Perform the "fuel system leak test". Refer to => [ Fuel System Leak Test ] Fuel System Leak Test.



- After completing the work, use the vehicle diagnostic tester to run the Check tank ventilation system for leaks guided function.