Fuel System, Checking For Leaks
Versions with fuel tank leak detection
Special tools and workshop equipment required
- Smoke Tester:VAS523005
- Connector:VAS523005/4
- Connection Set:VAS523005/5 , : VAS523005/6 or : VAS523005/7 (depending on the diameter of the breather line)
- Plugs:VAS523005/8
- Protective eyewear (yellow)
Connector Coupling Allocation
The connector couplings for fuel, vacuum and bleeder lines are color-coded. There is either a colored dot on the connector coupling, or the release button has the corresponding color. Refer to Color Coding .
Test Conditions:
- Guided Fault Finding was performed using the Vehicle Diagnostic Tester.
- A leak must have been detected by the Fuel Tank Leak Detection Module -GX36-.
TIP:
The "Small leak" DTC means that the total of all leaks is equal to a leak with a diameter greater than 1.0 mm.
Smoke Tester:VAS523005 application. Refer to Operating Instructions for Smoke Tester:VAS523005
Preparing the Smoke Tester:VAS523005
-- Check the water separator -A- on the smoke tester. If necessary, drain the water separator.
-- Connect the pressure hose to the connection -B-.
-- Use the dipstick -D- to check if there is enough fluid in the smoke tester.
-- Connect the power supply -C- for the smoke tester to the jump start points in the vehicle.
-- Remove the right underbody trim panels in the center and front. Refer to OVERVIEW - UNDERBODY TRIM PANELS .
-- Disconnect the breather line -arrow- on the underbody and check which connecting cable set should be used. Disconnect the connector couplings. Refer to CONNECTOR COUPLINGS, DISCONNECTING .
Check the Smoke Tester and Connection Set for Leaks:
-- Connect the connector -A- and connection set -B- as shown.
-- Open the shut-off valve -C-.
-- Connect the measuring hose from the smoke tester to the hose -D-.
-- Set the valve -A- to "TEST".
-- Switch on the Smoke Tester:VAS523005 -B-.
- The connection set will then be filled with smoke.
-- Watch the pressure gauge -C- and the flow meter -D-.
- If the pressure rises to 35 mbar (0.5 PSI) and the ball in the flow meter sinks to >>zero<<, then there are no leaks in the smoke tester and the connection set and they can be used.
-- Switch off the smoke tester.
Check the EVAP Canister Purge Regulator Valve 1 -N80- for Leaks:
-- Connect the connection set between the breather lines -1 and 2- on the vehicle as shown.
-- Connect the measuring hose from the smoke tester to the connecting piece -3-.
-- Close the shut-off valve -A- (line to the EVAP canister) -arrow-.
-- Set the valve -A- to "TEST".
-- Switch on the Smoke Tester:VAS523005 -B-.
- The hose to the EVAP Canister Purge Regulator Valve 1 -N80- will now be filled with smoke.
-- Watch the pressure gauge -C- and the flow meter -D-.
- If the pressure rises to 35 mbar (0.5 PSI) and the ball in the flow meter sinks to >>zero<<, then the EVAP Canister Purge Regulator Valve 1 has no leaks and is OK.
-- Switch off the smoke tester.
Checking the EVAP canister, fuel tank, and lines for leaks:
-- Open the shut-off valve -A- (line to the EVAP canister) -arrow-.
-- Remove the right rear wheel housing liner. Refer to OVERVIEW - REAR WHEEL HOUSING LINER .
-- Remove the vent line with air filter for the Fuel Tank Leak Detection Module -GX36-. Refer to VENT LINE WITH FILTER, REMOVING AND INSTALLING .
-- Fill the fuel system with smoke by setting valve -A- to "SMOKE" -arrow- and switching on the Smoke Tester:VAS523005 .
-- Allow the fuel system to fill with smoke until smoke escapes from the connection -arrow- on the detection pump -1-.
-- Once smoke escapes, seal the connection with a Plug:VAS523005/8 .
-- Set the valve -A- to "TEST" -arrow- and continue filling the fuel system.
-- Watch the pressure gauge -C- and the flow meter -D-.
- If the pressure rises to 35 mbar (0.5 PSI) and the ball in the flow meter sinks below the >>0.25 mm mark<< -arrow-, then the fuel system is filled.
TIP:
- If a sporadic fault is detected, move the lines, hoses, and caps. If the flow meter indicates a change when a component is moved, check that component.
- Depending on the fuel level in the fuel tank, it may take up to five minutes to fill with smoke.
- The Smoke Tester:VAS523005 has an automatic shut-off system. The smoke tester may need to be switched on again if it shuts off.
-- Once the flow meter has stabilized, switch the smoke tester off and check the pressure gauge.
- The pressure must not drop below 30 mbar (0.4 PSI) after five minutes.
If the pressure drops or no pressure builds, locate the leak as follows:
-- Set the valve -A- to "SMOKE" -arrow- and fill the fuel system with smoke.
- Check all the lines, hoses and the fuel filler cap for escaping smoke.
- Shine a flashlight on all components and hoses, because the smoke is more visible in white light.
- Use the laser to narrow down the location of the leak. The laser beam will >>light up<< in the smoke and be visible.
- The smoke contains a contrast agent. The contrast agent will be visible at the location of the leak under ultraviolet light.
- To check the sealing flange for the fuel delivery unit the sealing flange cover must be installed in the vehicle interior. To do so remove the bench seat. Refer to REAR BENCH SEAT, REMOVING AND INSTALLING .
-- Replace any leaking hoses or components.
After completing the work, perform the Check tank ventilation system for leaks guided function using the Vehicle Diagnostic Tester.
Tightening Specifications
- Refer to OVERVIEW - UNDERBODY TRIM PANELS .
- Refer to OVERVIEW - REAR WHEEL HOUSING LINER .