Tank Leak Diagnosis, Performing (Vehicles Through My 2012)

WARNING: This page does not describe the selected car, but rather 16 other vehicles, including the 2016 Audi S4, 2016 Audi A4 Quattro, 2016 Audi A4, 2015 Audi S4, and 2015 Audi A4 Quattro. However, it is still accessible from the selected car via links, so may be relevant.

Diagnostic leak test occurs in Guided Fault Finding , see Vehicle Diagnostic Tester.

Checking the Fuel Tank System and Tank Ventilation System 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.

-- Turn off the ignition.

-- Check whether the fuel filler cap -2- from the fuel tank was completely sealed for the test.

Fig 1: Identifying Cap -2-

Courtesy of AUDI OF AMERICA, LLC

-- Check if the cap seal to the fuel filler neck -1- was damaged or crimped and if it must be replaced.

NOTE:

Ignore item -3-.

-- Remove the rear bench seat. Refer to SEAT BENCH/SINGLE SEAT, REMOVING AND INSTALLING .

Fig 2: Identifying Cover Bolts For Locking Flange

Courtesy of AUDI OF AMERICA, LLC

-- Remove the locking flange cover -arrows-.

NOTE:

Observe installation notes for locking flanges. Refer to Installing and Installing .

-- Check if the sealing rings under the locking flanges are OK or if the locking rings on the locking flange are tightened correctly on the fuel tank. Also check the fuel line connections.

-- Visually check all lines and hose connections on the fuel system and replace leaking lines such as:

Line from EVAP canister to EVAP Canister Purge Regulator Valve 1 -N80-
Lines from EVAP canister to Leak Detection Pump -V144-.
Line from fuel tank to EVAP canister (below heat shield for EVAP canister).
Lines for tank ventilation (beneath right rear wheel housing liner).
Fuel lines to engine.

NOTE:

Leaks at lines and components of tank system can sometimes be located using a nonflammable, environmentally compliant leak detection spray. For this, initiate leak diagnostic several times in sequence to build up pressure in the system. At leaking areas, bubbles will form.

-- Perform a visual inspection on the fuel system components and tank ventilation system:

Fuel tank
EVAP canister
Leak Detection Pump -V144-
EVAP Canister Purge Regulator Valve 1 -N80-

NOTE:

Due to the form or function of the components, leaking areas may not always be localized by spraying on leak detection spray. In this case, clamp off lines to the relevant component using Hose Clamps - Up To 25mm3094 and initiate tank leak diagnosis. If the leak is no longer indicated, the component that was clamped off is defective. If clamped off directly at the leak detection pump and a leak is still indicated, the leak detection pump itself is leaking.