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.