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 diagnosis, testing and information system (VAS 5051B)
• Fuel system tester (smoke tester) (KLI 9210)
• Adapter hose (KLI 9210/55-1)
Test Conditions
• A leak was detected by the Leak Detection Pump (LDP).
• The "Guide Fault Finding" was performed with the (VAS 5051B).
(KLI 9210) Preparation
• Depending on the version, the appearance of the (KLI 9210) may vary.
- Check the (KLI 9210) to see whether there is enough fluid in the smoke generator.
- Set the valve - D - to "Hold".
- Open the nitrogen bottle - H -.
- Connect the measuring hose - G - on to the self test connection - B -.
- Set the valve - D - to "Test".
- Using the pressure reducer - J -, adjust the pressure to 10 in. H2O (25 mbar).
- 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.
Test Sequence
- Read the safety precautions before beginning work. Refer to --> [ Safety Precautions ] Safety Precautions.
- Observe the rules for cleanliness. Refer to --> [ Clean Working Conditions ] Clean Working Conditions.
- Disconnect the vent line - 1 - from the supply location.
• Press the securing ring to disengage the line.
- Connect the (KLI 9210/55-1) to the ventilation line - A - as shown.
- Connect the measuring hose - G - from the (KLI 9210) to the (KLI 9210/55-1).
- Set the valve - D - to "Hold".
- Connect the (VAS 5051B) - 1 - as follows:
- Connect the diagnostic cable - 2 - to the Data Link Connector (DLC) in the driver footwell.
- Start the engine and run at idle speed.
- Select the Guided Functions on the (VAS 5051B).
- Select "Guided Function" Check tank ventilation system for leaks.
- Activate the test.
- While the test runs, observe the pressure gauge on the (KLI 9210):
• The Leak Detection Pump (LDP) must pump the fuel system pressure up to at least 7 in. H2O (18 mbar).
If 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 LDP vacuum supply. Refer to --> [ Leak Detection Pump, Checking Vacuum Supply ] Leak Detection Pump, Checking Vacuum Supply.
If the minimum pressure is not reached and the pressure reached decreases immediately:
- Clamp off the hose to the Evaporative Emission (EVAP) canister purge regulator valve using the (3094).
- Repeat the test.
If the minimum pressure is not reached:
- Replace the EVAP canister purge solenoid valve 1.
If 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:
- Clamp off the hose to the EVAP canister purge regulator valve using the (3094).
If the pressure no longer drops now:
- Replace the EVAP canister purge solenoid 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 the valve - D - to "Test". Increase the present pressure up to 10 in. H2O (25 mbar).
- Observe the pressure gauge - C - and flow meter - E -. The fuel system is filled if the flow quantity decreases and the pressure increases to 10 in. H2O (25 mbar).
• 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 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 for leaks. Clamp off the hose to the EVAP canister purge regulator valve using the (3094).
- Repeat the pressure test by resetting the valve - D - to " Test".
- Observe the pressure gauge - C - and flow meter - E -:
• The fuel system is filled if the flow quantity decreases and the pressure increases to 10 in. H2O (25 mbar).
- After the pressure has stabilized, set the valve - D - to " Hold".
If the pressure no longer drops now:
- Replace the EVAP canister purge solenoid 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, perform the Guided Functions, Check tank ventilation system for leaks using the (VAS 5051B).