Fuel/EVAP System through 08.06, Checking for Leaks
Fuel/EVAP System through 08.06, Checking for Leaks
=> [ EVAP System Overview ]
=> [ Leak Detection Pump, Checking Pressure Buildup ]
=> [ Leak Detection Pump, Checking Vacuum Supply ]
Special tools, testers and auxiliary items required
• Fuel System Tester (Smoke Tester) (KLI 9210)
• Hose Adapter (KLI 9210/55-2)
• Vehicle Diagnosis, Testing and Info. System (VAS 5051B), (VAS 5052) or (VAS 5053)
• Hose Clamps Up to 25 mm Dia. (3094)
Conditions
• A leak was detected by the Leak Detection Pump (LDP) (V144).
• Guided fault finding was performed using the vehicle diagnostic tester.
(KLI 9210) Preparation:
• Depending on the version, the appearance of the (KLI 9210) may vary.
- Check the (KLI 9210) to determine 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 - 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 a min. 2 minutes. If the pressure is not maintained, check the tester.
Fuel System, Checking for Leaks:
- Disconnect the ventilation line - arrow - to the Evaporative Emission (EVAP) canister purge regulator valve (N80) in the engine compartment.
- Connect the (KLI 9210/55-2) - A - as shown between the EVAP canister purge regulator valve and ventilation line.
- Connect the measuring hose from the (KLI 9210) to the (KLI 9210/55-2).
- Connect the (KLI 9210) to the vehicles battery.
- Connect the vehicle diagnostic tester to the vehicle.
- Start the engine and run at idle speed.
- Select the OBD button on the vehicle diagnostic tester.
- Select diagnostic mode 8 "Tank leak test".
- Select "Tank leak test" entry and press right arrow button > to activate the test.
• When diagnostic mode 8 "Tank leak test" is activated, the leak detection pump and EVAP canister purge solenoid valve 2 (N115) are closed for a maximum of 1000 seconds. The EVAP canister purge regulator valve is not activated. The entire system is now closed.
• If the Engine Control Module (ECM) stops the test, it can be reactivated by stopping the engine and restarting.
- Set the valve - D - to "Test". The fuel system is now filled with nitrogen.
- 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 no pressure decrease can be determined, end diagnostic mode 8 and check the LDP pressure buildup. Refer to => [ Leak Detection Pump, Checking Pressure Buildup ].
If pressure does not build up or if positive pressure is not maintained for at least 5 minutes, locate the leak as follows:
Allow the engine to continue running in idle, with diagnostic mode 8 activated.
- First check the EVAP canister purge regulator valve for leaks. Clamp off the hose to the EVAP canister purge regulator valve using the (3094) - arrow -. See also - item A -.
- 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 pressure now no longer falls, replace the EVAP canister purge regulator valve.
If the 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 visible fuel system lines and hoses for escaping smoke. Also check fuel tank sealing 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 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.
If no malfunctions are detected:
- Remove the right rear wheel housing liner.
If smoke comes out of the air filter housing - item 7 -:
- Clamp off the hose between the EVAP canister purge solenoid valve 2 and air filter housing - arrow -. See also - item B -.
- Observe the air filter. If no smoke comes out of it now, the EVAP canister purge solenoid valve 2 leaks. Replace the EVAP canister purge solenoid valve 2.
If smoke still comes out of the air filter housing:
- Clamp off the hose between the LDP and air filter - arrow -. See also - item C -.
- Observe the air filter. If no smoke comes out of it now, the shut off valve in the LDP leaks. Replace the LDP.
If no smoke comes out of the air filter housing - item 7 -:
- Check all fuel system components and hoses for escaping smoke.
To check the fuel pump and fuel filter flange, the assembly opening in the vehicle interior must be opened.
- Replace leaking hoses or components.
After completing the work, perform the "Check tank ventilation system for leaks" guided function using the vehicle diagnostic tester.
EVAP System Overview
1 - Evaporative Emission (EVAP) Canister
2 - Adapter Hose (KLI 9210/55-2) Installed Location
• Used for the fuel system, checking for leaks procedure.
3 - Evaporative Emission (EVAP) Canister Purge Regulator Valve 1 (N80)
4 - Vent Line
• To the intake manifold.
5 - Solenoid valve
• For the leak detection pump.
6 - Vacuum Line
• To the intake manifold.
7 - Air Filter Housing
• For the leak detection pump.
8 - Leak Detection Pump (LDP) (V144)
9 - Fuel Tank
10 - Cap
11 - Evaporative Emission (EVAP) Canister Purge Regulator Valve 2 (N115)
12 - Pressure Retention Valve
Arrow A - Clamp Off Here
• Used for the fuel system, checking for leaks procedure.
• To check the EVAP canister purge regulator valve 1.
Arrow B - Clamp Off Here
• Used for the fuel system, checking for leaks procedure.
• To check the EVAP canister purge regulator valve 2.
Arrow C - Clamp Off Here
• Used for the fuel system, checking for leaks procedure.
• To check the leak detection pump.
Leak Detection Pump, Checking Pressure Buildup
Conditions
• (KLI 9210) and (KLI 9210/55-2) still connected to the vehicle.
• Valve - D - is at "Hold"
• Diagnostic mode 8 ended and the vehicle running at idle
Fuel system must have no pressure for the test. To release the residual pressure, proceed as follows:
- Briefly open the quick release coupling - arrow - on the (KLI 9210/55-2) to release pressure in the fuel system. The pressure gauge on the (KLI 9210) must drop to 0 in. H2O.
- Select Guided Functions operating mode on the vehicle diagnostic tester.
- Select "Check tank ventilation system for leaks" guided function.
- Activate the test.
- Observe the pressure gauge on the (KLI 9210) while the test is running.
- The Leak Detection Pump (LDP) (V144) must pump the fuel system pressure up to at least 7 in. H2O (17 mbar).
- If the pressure is not reached, check the LDP vacuum supply. Refer to => [ Leak Detection Pump, Checking Vacuum Supply ].
- If the fuel system has no leaks and the LDP vacuum supply is OK, replace the LDP.
Leak Detection Pump, 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 (LDP) (V144) installed location: inside the right rear wheel housing under the liner.
- Remove the right rear wheel and wheel housing liner.
- Loosen the Evaporative Emission (EVAP) canister bolts - item 14 -=> [ Bolt ] Evaporative Emission System, through 08.06 and lower it so the vacuum line is more easily accessible.
CAUTION!
Support the EVAP canister so it does not hang by the hoses and lines. This prevents damage.
- Disconnect the vacuum line - 1 - from the LDP.
- Connect the (V.A.G 1397A) with the T-piece and 6 mm diameter hose between the vacuum line - 1 - and the LDP - 2 -.
- Turn on measuring range I (absolute pressure measurement).
- Connect the vehicle tester and start the engine.
- Select Guided Functions operating mode on the vehicle diagnostic tester.
- Select "Check tank ventilation system for leaks" guided function.
- While the test is running, observe the display on the (V.A.G 1397A).
• The pressure must pulsate and must not rise above 0.700 bar 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.