Fuel System, Checking For Leaks
Fuel System, Checking for Leaks
=> [ Fuel System Leak Test ]
=> [ EVAP System Functional Overview ]
=> [ Leak Detection Pump (V144), Checking Vacuum Supply ]
Special tools, testers and auxiliary items required
• Evaporative Emissions Tester (KLI 9210)
• Adapter for EVAP. Tester (KLI 9210/55-1)
• Vehicle Diagnostic Tester
• Hose Clamps up to 25 mm Dia. (3094)
The connectors for the fuel, vacuum and ventilation lines are color coded. There is either a colored dot on the connector or the release button is the corresponding color.
Test Conditions
• The leak detection pump detected a leak.
• Perform "Guided Fault Finding" using the vehicle diagnostic tester.
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".
- Adjust the pressure to 25 mbar (10 in H2O) using the pressure reducer - J -.
- Set the valve - D - to "Hold".
- The pressure must now be maintained a minimum of 2 minutes. If the pressure is not maintained, check the tester.
Fuel System, Checking for Leaks
- Connect the adapter for EVAP. tester (KLI 9210/55-1) to the vent line - A -. (Color identification: white).
- Connect the measuring hose - G - from the evaporative emissions tester (KLI 9210) to the adapter for EVAP. tester (KLI 9210/55-1).
- Set the valve - D - to "Hold".
- Connect the vehicle diagnostic tester - 1 - to the vehicle.
- Start the engine and let it run in idle.
- Select the Guided Functions mode in the vehicle diagnostic tester.
- Select "Check fuel tank ventilation system for leaks" under "Guided Functions ".
- Start the test.
- Watch the pressure gauge on the evaporative emissions tester (KLI 9210).
• The leak detection pump must pump the fuel system up to minimum of 7 in. H2O (18 mbar).
If the he minimum pressure is not reached, but the pressure reached does not decrease:
- Turn off the ignition and perform a pressure retention test. If there is no decrease in pressure, check the vacuum supply for the leak detection pump, Refer to => [ Leak Detection Pump (V144), Checking Vacuum Supply ].
If the minimum pressure is not reached and the pressure reached decreases immediately:
- Clamp off the hose to the EVAP canister purge regulator valve 1 using a hose clamp up to 25 mm dia. (3094) - arrow -.
- Repeat the test. If the minimum pressure was reached, replace the EVAP canister purge regulator 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 ].
If the minimum pressure is reached, turn the ignition off.
The valve in the leak detection pump is now closed and the pressure is maintained.
- Watch the pressure gauge:
If the pressure does not decrease, perform a pressure retention test to locate any possible pinhole leaks.
If the pressure falls, clamp off the hose to the EVAP canister purge regulator valve 1 using a hose clamp up to 25 mm dia. (3094) - arrow -.
- If the pressure stops falling, replace the EVAP canister purge regulator valve 1.
If the pressure continues to fall, perform the "Fuel System, Leak Test", refer to => [ Fuel System Leak Test ].
Pressure Retention Test
- Set the valve - D - to "Test". Increase the current pressure to 25 mbar (10 in. H2O).
- Watch the pressure gauge - C - and the 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 the valve - D - to "Hold".
• After 5 minutes the pressure must not drop below 8 in. H2O (20 mbar).
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. Clamp off the hose to the EVAP canister purge regulator valve 1 using a hose clamp up to 25 mm dia. (3094) - arrow -.
- Set the valve - D - to "Test" and repeat the pressure test.
- Watch the pressure gauge - C - and the 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 the valve - D - to "Hold".
- If the pressure stops falling, replace EVAP canister purge regulator valve 1.
If the pressure continues to fall, perform the "Fuel System, Leak Test". Refer to => [ Fuel System Leak Test ].
After completing the work, perform the guide function "Check tank ventilation system for leaks" using the vehicle diagnostic tester.
Fuel System Leak Test
Test Conditions
• The procedure "Fuel System, Checking for Leaks" was performed. Refer to => [ Fuel System, Checking for Leaks ] Testing and Inspection.
• The evaporative emissions tester (KLI 9210) with the adapter for EVAP. tester (KLI 9210/55-1) is connected to the vehicle
- Connect the evaporative emissions tester (KLI 9210) to the vehicles battery.
- Remove the right rear wheel housing liner..
- Clamp off the hose between the leak detection pump and the air filter using a hose clamp up to 25 mm dia. (3094) - arrow -.
- 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 10 in. H2O, then the fuel system is full.
- After the pressure has stabilized, set the valve - D - to "Hold".
• After 5 minutes the pressure must not drop below 8 in. H2O (20 mbar).
- If the pressure stops falling, replace the leak detection pump.
If the pressure is not maintained for a minimum of 5 minutes or if no pressure is built up, localize the leak as follows:
- Set the valve - D - to "Test" and fill the system with smoke.
- While the fuel system is being filled, press the 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.
• Illuminate components and hoses with a strong flood light, the smoke will be more visible.
• To check for leaks at accessible locations, also use a ultrasonic measuring device or commercially available leak detection spray.
• Depending on how long the fault finding lasts, the smoke generator button may need to be pressed again. This ensures there is enough smoke present in the fuel system.
• To check the fuel pump and fuel delivery unit flange, the assembly openings in the vehicle interior must be opened.
- Replace any leaking hoses or components.
After completing the work, perform the guided function "Check tank ventilation system for leaks" using the vehicle diagnostic tester.
EVAP System Functional Overview
1 Evaporative Emission (EVAP) Canister
2 Adapter for EVAP. Tester (KLI 9210/55-1) Installed Location
• Used during the fuel system leak test.
3 EVAP Canister Purge Regulator Valve 1 (N80)
4 Vent Line
• Throttle valve control module (J338)
5 Solenoid Valve
• For the leak detection pump.
6 Vacuum Line
• To the intake manifold.
7 Air Filter
• For the leak detection pump.
8 Leak Detection Pump (V144)
9 Fuel Tank
10 Cap
Leak Detection Pump (V144), Checking Vacuum Supply
Special tools, testers and auxiliary items required
• Turbocharger Tester (V.A.G 1397A)
• T-Piece (251 201 346)
• 6 mm Diameter Hose
• Leak detection pump installed location: inside the right rear wheel housing, under the liner.
- Remove the wheel and the right rear wheel housing liner..
- Disconnect the vacuum line - 1 - from the leak detection pump.
- Connect the turbocharger tester (V.A.G 1397A) , using the T-piece and 6 mm diameter hose, between the vacuum line - 1 - and the leak detection pump - 2 -.
- Turn on the measuring range I (absolute pressure measuring).
- Connect the vehicle diagnostic tester and start the engine.
- Select the Guided Functions mode in the vehicle diagnostic tester.
- Select "Check fuel tank ventilation system for leaks" under guided functions.
- Start the test.
- Watch the display on the evaporative emissions tester (V.A.G 1397A) while the test is running.
• The pressure must pulsate and must not rise above 0.700 bar (absolute pressure) during the test.
- If the pressure rises above 0.700 bar during the test, the vacuum supply is too low. Make sure the vacuum line to the intake manifold is not kinked or plugged up.