Fuel System, Checking for Leaks
Fuel System, Checking for Leaks
=> [ Fuel System Leak Test ]
=> [ EVAP System Function Overview ]
=> [ Leak Detection Pump Vacuum Supply, Checking ]
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.
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 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 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 ventilation line - A - as shown. (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 valve - D - to "Hold".
- Connect the vehicle diagnostic tester - 1 - to the vehicle.
- Start the engine and run at idle speed.
- Select Guided Functions on the vehicle diagnostic tester.
- Select "Check tank ventilation system for leaks".
- Start the test.
- While the test runs, observe the pressure gauge on the evaporative emissions tester (KLI 9210).
• The leak detection pump must pump the fuel system up to a minimum of 7 in. H2O (18 mbar).
If the minimum pressure is not reached, but the pressure reached does not decrease:
- Turn the ignition off and perform a pressure retention test. If no decrease in pressure is observed: Check the leak detection pump 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 is not 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".
If the minimum pressure is reached, turn off the ignition.
The valve in the leak detection pump is now closed and the pressure is maintained.
- Observe the pressure gauge:
If the pressure does not decrease, perform a pressure retention test to locate any possible pinhole leaks.
If the pressure decreased, 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 now no longer falls, replace the EVAP canister purge regulator valve 1.
If the pressure still decreases, perform the "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 8 in. H2O (20 mbar).
If the pressure is not maintained for 5 minutes, the leak should be localized as follows:
- First, check 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 -.
- 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 the 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 now no longer falls, replace the EVAP canister purge regulator valve 1.
If the pressure still decreases, perform the "Fuel System Leak Test".
After completing the work, perform the "Check tank ventilation system for leaks" guided function using the vehicle diagnostic tester.
Fuel System Leak Test
Conditions
• The procedure "Fuel System, Checking for Leaks" was performed.
• The evaporative emissions tester (KLI 9210) and the adapter for EVAP. tester (KLI 9210/55-1) are 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 - arrow - between the leak detection pump and air filter housing using a hose clamp up to 25 mm dia. (3094).
- Set 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".
• After 5 minutes the pressure must not drop below 8 in. H2O (20 mbar).
- If the pressure no longer decreases, 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:
- Fill the fuel system with smoke by setting 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 filling with smoke.
- Check all the fuel system lines and hoses for leaking smoke. Also check the fuel 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 need to be pressed again. This ensures there is enough smoke present in the fuel system.
• To check the fuel pump and fuel filter flange, the assembly openings 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 Function Overview
1 Evaporative Emission (EVAP) Canister
2 Adapter for EVAP. Tester (KLI 9210/55-1) Installed Position
• Used during the fuel system leak test.
3 EVAP Canister Purge Regulator Valve 1 (N80)
4 Vent Line
• To the throttle valve control module.
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 (V144)
9 Fuel Tank
10 Cap
Leak Detection Pump Vacuum Supply, Checking
Special tools, testers and auxiliary items required
• Turbocharger Tester (V.A.G 1397 A)
• T-Connection (251 201 346)
• 6 mm Diameter Hose
• Leak detection pump installed location: Inside the right rear wheel housing, under the liner.
- Remove the right rear wheel and wheel housing liner.
- Disconnect the vacuum line - 1 - from the leak detection pump.
- Connect the turbocharger tester (V.A.G 1397 A) with the T-piece and 6 mm diameter hose between the vacuum line - 1 - and the leak detection pump - 2 -.
- Turn on measuring range I (absolute pressure measurement).
- Connect the vehicle diagnostic tester and start the engine.
- Select Guided Functions on the vehicle diagnostic tester.
- Select "Check tank ventilation system for leaks".
- Start the test.
- While the test is running, observe the display on the turbocharger tester (V.A.G 1397 A).
• 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.