Leak Detection Test, Performing - Audi Q7 2007 Repair Manual

Audi Q7 2007 ➤
Fuel Supply System - Edition 10.2018
then moved out so that the reed contact at the operating rod
remains in the "Open" position.
♦ During leak diagnosis, the reed contact is monitored to check
if it remains open within 15 seconds. This indicates the system
is sealed.
♦ If pressure falls (indicating a leak), the diaphragm moves back
and the reed contact closes.
♦ If the reed contact closes within 15 seconds of detection time,
a further test is performed: In this case the diaphragm pump
pumps 4 times again. The engine control module (ECM)
measures the time for each of the 4 pumps until the reed con‐
tact is closed again. From that, the control module can recog‐
nize a "Small leak" (smaller than 1 mm in diameter) or a "Large
leak".
The leak detection is activated automatically shortly after each
cold engine start (under 35 °C) and drive at a speed faster than
10 km/h. If there is an incorrect measurement, an entry is stored
in the engine control module DTC memory. The Malfunction In‐
dicator Lamp (MIL) in the instrument cluster lights up if the mal‐
function is recognized for 2 subsequent starts. Diagnosis can also
be activated using a Vehicle Diagnostic Tester. Refer to
⇒ "4.5 Leak Detection Test, Performing", page 64
Note
After the cold start, the leak detection can repeated up to 10
♦
times within the first 20 minutes.
It can be determined if an automatic leak diagnosis was re‐
♦
cently performed with the -Vehicle Diagnostic Tester- connec‐
ted in measured values block 071. Refer to
⇒ "4.5 Leak Detection Test, Performing", page 64
4.5

Leak Detection Test, Performing

Check the fuel tank lead diagnostic system in
-Vehicle Diagnostic Tester- .
Finding
Tank System and Tank Ventilation System, Checking for Leaks
Note
The following describes individual areas in the fuel supply and
♦
ventilation systems where leaks are possible. After repairing
a possible leak, perform a leak test to ensure that leak was
successfully repaired.
Secure all hose connections with hose clamps of the same
♦
type as those equipped by the factory. Refer to the Parts Cat‐
alog.
Replace seals and gaskets when performing repair work.
♦
– Switch off ignition.
– Check whether the fuel filler cap of the fuel tank was com‐
pletely sealed for the test.
– Check whether seal of fuel filler cap was damaged or crimped.
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Rep. Gr.20 - Fuel Supply
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Guided Fault