Fuel/EVAP System, Checking for Leaks
Fuel/EVAP System, Checking for Leaks, Engine Codes BGP, BGQ, CBTA and CBUA
--> [ Fuel System Leak Test ]
--> [ EVAP System Function Overview ]
--> [ Leak Detection Pump, Checking Vacuum Supply ]
Special tools, testers and auxiliary items required
• Fuel system tester (smoke tester) (KLI 9210)
• Hose adapter (KLI 9210/55-1)
• Vehicle diagnosis, testing and information system (VAS 5051B), (VAS 5052) or (VAS 5053)
• Hose clamps up to 25 mm diameter (3094)
Test Conditions
• A leak was detected by the Leak Detection Pump (LDP).
• "Guided Fault Finding" was performed with the (VAS 5051B).
Evaporative Emissions Tester (KLI 9210) Preparation:
• Depending on the version, the appearance of the (KLI 9210) may vary.
- Check the (KLI 9210) to see if 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 10 in. (25 mbar). H2O).
- 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 (KLI 9210/55-1) - B - to the ventilation line - A - as shown.
- Connect the measuring hose from the (KLI 9210) to the (KLI9210/55-1).
- Connect the (KLI 9210) to the vehicle battery.
- Connect the (VAS 5051B) to the vehicle.
- Start the engine and run at idle speed.
- Select Guided Functions operating mode on the (VAS 5051B).
- Select "Check tank ventilation system for leaks" guided function.
- Activate the test.
- While the test runs, observe the pressure gauge on the (KLI 9210).
• The LDP must pump the fuel system pressure up to at least 18 mbar (7 in. H2O).
The minimum pressure is not reached, but the pressure reached does not decrease:
- Check the LDP vacuum supply. Refer to --> [ Leak Detection Pump, Checking Vacuum Supply ].
The minimum pressure is not reached and the pressure reached decreases immediately:
- There is a leak in the fuel system, perform the fuel system test. Refer to --> [ Fuel System Leak Test ].
If the pressure is reached, switch the ignition off.
• The valve in the LDP is now closed and the pressure is maintained.
- Set the valve - D - to "Test". Increase the present pressure up to 25 mbar (10 in. H2O).
- Observe the pressure gauge - C - and flow meter - E -. If the flow quantity decreases and pressure increases to 25 mbar (10 in. H2O), fuel system is filled.
• 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 is not maintained for 5 minutes, the leak should be localized as follows:
- First check the Evaporative Emission (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 valve - D - to " Test".
- Observe the pressure gauge- C - and flow meter - E -. If the flow quantity decreases and pressure increases to 25 mbar (10 in. H2O), fuel system is filled.
- After the pressure has stabilized, set the valve - D - to " Hold".
- If pressure now no longer falls, replace the EVAP canister purge regulator valve.
If pressure still drops:
- Remove the right rear wheel housing liner.
- Clamp off the hose between the LDP and the air filter - arrow -.
- Reset the valve - D - to "Test".
- Observe the pressure gauge - C - and flow meter - E -. If the flow quantity decreases and pressure increases to 25 mbar (10 in. H2O), fuel system is filled.
• 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 no longer decreases, replace the LDP.
If pressure still drops:
- Reset the valve - D - to "Test".
- 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 tank fill 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 have 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 "Check tank ventilation system for leaks" guided function using.
Fuel System Leak Test
Test Conditions
• (KLI 9210) with the (KLI 9210/55-1) connected to the vehicle
- Remove the right rear wheel housing liner.
- Clamp off the hose between the Leak Detection Pump (LDP) and the air filter - arrow -.
- Set the valve - D - to "Test".
- 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 fuel tank fill 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 have 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 the leaking hoses or components.
After completing the work, perform the "Check tank ventilation system for leaks" guided function using.
EVAP System Function Overview
1 Evaporative Emission (EVAP) canister
2 Adapter hose (KLI 9210/55-1) installation location
• With the leak test in fuel system.
3 EVAP canister purge regulator valve (N80)
4 Vent line
• To the throttle valve control module.
5 Solenoid valve
• For the Leak Detection Pump (LDP).
6 Vacuum line
• To the intake manifold.
7 Air filter housing
• For the LDP.
8 Leak Detection Pump (LDP) (V144)
9 Fuel tank
10 Cap
Leak Detection Pump, Checking Vacuum Supply
Special tools, testers and auxiliary items required
• Turbocharger tester (VAG 1397A)
• T-piece (251 201 346)
• 6 mm diameter hose
• Leak Detection Pump (LDP) component location: Under the wheel housing liner in the right rear wheel housing.
- Remove the right rear wheel and wheel housing liner.
- Remove the vacuum line - 1 - from the LDP - 2 -.
- Connect the (VAG 1397A) with the T-piece and 6 mm diameter hose between the vacuum line - 1 - and the LDP - 2 -.
- Switch on the measuring range I (absolute pressure measurement).
- Connect the (VAS 5051B) and start the engine.
- Select Guided Functions operating mode.
- Select "Check tank ventilation system for leaks" guided function.
- Activate the test.
- While the test is running, observe the display on the (VAG 1397A).
• 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. Check the vacuum line to the intake manifold for kinks or blockages.