Fuel System, Checking For Leaks
Fuel System, Checking for Leaks
Special tools, testers and auxiliary items required
• Fuel System Tester (Smoke Tester) (KLI 9210)
• Hose Adapter (KLI 9210/55-1)
• Vehicle Diagnostic Tester
• Hose Clamps up to 25 mm Diameter (3094)
Test Conditions
• A leak was detected by the Leak Detection Pump (LDP) (V144).
• Guided fault finding was performed with the vehicle diagnosis, testing and information system.
(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 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 (KLI 9210/55-1) to the ventilation line - A - as shown.
- Connect measuring hose - G - from the (KLI 9210) to the (KLI 9210/55-1).
- Set valve - D - to "Hold".
- Connect the vehicle diagnosis, testing and information system to the vehicle.
- Start engine and run at idle speed.
- Select Guided Function operating mode on vehicle diagnostic tester.
- Select "Check tank ventilation system for leaks" guided function.
- Activate test.
- While the test runs, observe pressure gauge on (KLI 9210).
• The LDP must pump the fuel system pressure up to at least 7 in. H2O (18 mbar).
The minimum pressure is not reached, but the pressure reached does not decrease:
- Switch ignition off and perform pressure retention test, refer to. If no drop in pressure is detected: check the vacuum supply from the LDP. Refer to => [ Leak Detection Pump, Checking Vacuum Supply ].
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 (N80) with a hose clamp - arrow -.
- Repeat the test. If the minimum pressure is now reached: replace the EVAP canister purge regulator valve.
The minimum pressure is not reached again and the pressure reached decreases immediately:
- There is a leak in the fuel system. Perform a fuel system leak test. Refer to => [ Fuel System Leak Test ].
If the minimum pressure is reached, switch ignition off.
The valve in the LDP is now closed and the pressure is maintained.
- Observe 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 hose to the EVAP canister purge regulator valve with a hose clamp - arrow -.
- If pressure now no longer falls, replace EVAP canister purge regulator valve.
If the pressure still decreases, perform leak test in fuel system. Refer to => [ Fuel System Leak Test ].
Pressure Retention Test
- Set valve - D - to "Test". Increase 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 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 EVAP canister purge regulator valve for leaks. Clamp off the hose to the EVAP canister purge regulator valve with a hose clamp - arrow -.
- Repeat pressure test by resetting valve - D - to " Test".
- Observe 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 valve - D - to " Hold".
- If pressure now no longer falls, replace EVAP canister purge regulator valve.
If the pressure still decreases, perform leak test in fuel system. Refer to => [ Fuel System Leak Test ].
After completing the work, perform check tank ventilation system for leaks guided function using the vehicle diagnosis, testing and information system VAS 5051.
Fuel System Leak Test
Test Conditions
• Procedure for checking fuel system for leaks performed. Refer to => [ Fuel System, Checking for Leaks ] Fuel System, Checking for Leaks.
• (KLI 9210) with (KLI 9210/55-1) connected to vehicle
- Connect the (KLI 9210) to the vehicle battery.
- Remove the rear right wheel housing liner.
- Clamp off hose between the Leak Detection Pump (LDP) (V144) and air filter - arrow -.
- Set 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 valve - D - to " Hold".
• After 5 minutes the pressure must not drop below H2O (20 mbar) drop.
- If the pressure no longer decreases, replace the LDP.
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 fuel system with smoke by setting valve - D - to " Test".
- While fuel system is being filled, press 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 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 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 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 tester.
EVAP System Function Overview
1 Evaporative Emission (EVAP) Canister
2 Adapter Hose (KLI 9210/55-1) Installed Location
• With leak test in fuel system.
3 Evaporative Emission (EVAP) Canister Purge Regulator Valve 1 (N80)
4 Vent Line
• Throttle valve control module (J338).
5 Solenoid Valve
• For the 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 (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 wheel housing liner.
- Remove rear right wheel and wheel housing liner.
- Remove vacuum line - 1 - from the LDP.
- Connect the (V.A.G 1397A) with T-piece and 6 mm diameter hose between vacuum line - 1 - and LDP - 2 -.
- Switch on measuring range I (absolute pressure measurement).
- Connect vehicle tester and start engine.
- Select Guided Function operating mode on vehicle diagnostic tester.
- Select "Check tank ventilation system for leaks" guided function.
- Activate test.
- While the test is running, observe display on (V.A.G 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 vacuum line to intake manifold for kinks or blockages.