Leak Detection, Activating and Troubleshooting
Observe Safety measures
Observe Rules of cleanliness
CAUTION! Always refer to the latest parts catalog to ensure that you use original equipment fuel hose clamps.
NOTE:
- Always replace O-rings, sealing rings and gaskets.
- Radiator fan must not come on during the test!
Troubleshooting requirements
- DTC memory checked and no DTCs stored
- All electrical consumers switched OFF
- A/C switched OFF
- Intake Air Temperature lower than 90 °C
See Display group 004, channel 4.
- Engine Coolant Temperature less than 95 °C
See Display group 004, channel 3.
- Throttle angle less than 10 °
See Display group 003, channel 3.
- Connect Scan Tool VAG1551/1552 to vehicle as shown using VAG1551/3 adaptor cable.
- Start engine and let idle.
- Press 1 button to select "Rapid data transfer"
Display will appear as:
Rapid data transfer HELP
Enter address word XX
- Press 0 and 1 buttons to select Address word 01: "Engine electronics"
- Press Q button to enter input.
- Press -> button.
Display will appear as:
Rapid data transfer HELP
Select Function XX
- Press 0 and 8 buttons to select Function 08: "Read measuring value block"
- Press Q button to enter input.
Display will appear as:
Read measuring value block
Enter display group number XXX
- Press 0, 7 and 1 buttons to select "display group 71"
- Press Q button to enter input.
Display will appear as:
Read measuring value block ->
Reed closed break Test OFF
NOTE:
- Condition for continuing test is "Reed closed" on the display.
- The display does not always show "Abort"
- If the display: "reed open" appears: Briefly open the filler cap to reduce pressure - this will close the reed contact. Continue checking as follows:
- Press 0 and 4 buttons to select Function 04: "Basic Setting"
Display will appear as:
System in basic adjustment 71 ->
Reed closed Test ON
- The EVAP canister valve is opened to allow pressure relief in the system.
- Then the LDP pump -V144 will be triggered.
- The total procedure lasts approx. 60 seconds.
- Press -> button.
Display will appear as:
System in Basic Adjustment 71 ->
Reed open Syst.Test Test ON
- The system makes a test, the LDP pump -V144 starts running and shuts off when the pump running time reaches a pre-determined time-out.
- The total procedure lasts approx. 60 seconds.
Display will appear as:
System in Basic Adjustment 71 ->
Reed open Measurement Test >ON
- Measurement phase begins. The LDP pump -V144 is switched off and the ECM checks whether the reed contact has closed within 10 seconds.
If NO
Display will appear as:
System in Basic Adjustment 71 ->
Reed open Messg. END Syst.OK
- The system is sealed and the measurement is ended.
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End output"
- Press Q button to enter input.
If contact does not close within 10 seconds
- The LDP pump -V144 performs 4 pump strokes. The ECM compares the time it takes to carry out the pump strokes and the time until the reed contact closes again.
- Display will appear as:
System in Basic Adjustment 71 ->
Reed clos fine leak Messg. ENDSyst.not OK
- The system has recognized a fine leak (phi greater than 1 mm).
Display will appear as:
System in Basic Adjustment 71 ->
Reed clos larg leak Messg. ENDSyst.not oK
- The Leak detection system has recognized a large leak.
- Press -> button.
If system has recognized a fine or large leak
- Check tank system and tank ventilation system for leaks. See below.
- Perform tank leak diagnosis again.
Fuel tank system and tank ventilation system, leak checking
NOTE: In the following, individual questionable points will be considered that could be leaks in the fuel tank and tank ventilation system. After eliminating a possible leak, it is effective to then perform a tank leak diagnosis to determine whether the leak was successfully sealed.
- Switch OFF ignition.
- Check if filler cap was completely closed for the test.
- Check if filler cap seal is damaged or crimped, replace if necessary.
- Check if the gaskets under the cover flanges are OK and if the union nut on the fuel tank cover flange is correctly tightened.
- Check hose connections for tightness and integrity repair or replace as necessary.
- Remove luggage compartment trim.
- Remove connector flange cover under luggage compartment trim.
NOTE: Observe the cover flange installation instructions.
- Visually inspect all fuel tank system line and hose connections and replace any leaking lines, for example:
- Line from EVAP canister to EVAP canister purge regulator valve in engine compartment.
- Lines from EVAP canister to the LDP pump (under left wheel house liner).
- Line from the fuel tank to the EVAP canister (under the cover for the EVAP canister).
- Lines of the tank ventilation system (under right wheel house liner).
- Fuel lines to the engine.
NOTE: Locate leaks at lines and components of the tank system by using a non-combustible, environmentally friendly, leak detector spray. Perform several leak diagnostics in a row to build up the system pressure. Bubbles will form at points of leakage.
- Visually inspect the fuel supply system components:
- Fuel tank
- EVAP canister
- LDP pump
- EVAP canister purge regulator valve -N80
NOTE:
- At times, the above components cannot be effectively leak tested using a leak detection spray, either because of component location or function. In such cases, clamp off the lines to the component involved and perform a leak check. If the leak is no longer displayed, the clamped off component is faulty. If the LDP pump is clamped off and there is still a leak displayed, the LDP pump is faulty.
- Check EVAP canister purge regulator valve -N80