Volkswagen Touareg (2003 year). Manual - part 30

Activated charcoal filter system

Function
Depending on the air pressure and ambient temperature, fuel va‐

pour will form above the level of fuel in the tank.
The activated charcoal filter system prevents these HC emissions

escaping to the atmosphere.
Fuel vapours pass from the highest point in the tank (on filler neck)

through the expansion tank and into the activated charcoal filter.
The activated charcoal stores these vapours like a sponge.
When the car is being driven and the Lambda control is active

(engine warm), the activated charcoal filter solenoid valve 1 -N80-

is activated (pulsed) by the engine control unit depending upon

load and engine speed. The opening period depends on the input

signals.
During the purging procedure (regeneration of activated char‐

coal), the intake manifold vacuum draws fresh air through the vent

of the activated charcoal filter. The fuel vapours stored in the ac‐

tivated charcoal and fresh air are fed to combustion in metered

quantities.
The activated charcoal filter solenoid valve 1 -N80- is closed when

it is not supplied with current (e.g. open circuit). The activated

charcoal filter will not be purged.

Note

♦

Hose connections are secured with either spring-type or

clamp-type clips.

♦

Spring-type clip pliers -VAS 6340- or spring-type clip pliers -

VAS 5024 A- are recommended for installation of spring-type

clips.

Observe safety precautions 

⇒ page 99

 .

Observe rules for cleanliness 

⇒ page 99

 .

Assembly overview - activated charcoal filter system

⇒ page 118

 .

Function of pressure retention valve 

⇒ page 118

Checking fuel system for leaks 

⇒ page 118

 .

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3. Activated charcoal filter system    

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Assembly overview - activated charcoal filter system

1 - Expansion tank
2 - Gravity valve
3 - To gravity valve
4 - Pressure retention valve

❑ Function 

⇒ page 118

 .

5 - 9 Nm
6 - Connecting hose
7 - Air filter

❑ Clean if soiled.

8 - Connector

❑ For breather line.

9 - Activated charcoal filter
10 - 9 Nm
11 - Connector
12 - Activated charcoal filter

solenoid valve 1 -N80-
13 - Rubber bracket
14 - To connection

❑ On intake manifold

15 - Breather line

Function of pressure retention valve
From gravity valve (on expansion tank) the pressure retention

valve is open in both directions of flow. -Arrow 1- is the side to

expansion tank.
On the other side it is only open for flow in one direction.

-Arrow 2- is the side to activated charcoal filter.

3.2

Checking fuel system for leaks

Special tools and workshop equipment required

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♦ Tester -V.A.G 1371-

Procedure:
– Remove rear right wheel and wheel housing liner.
– Clamp off hose -arrow- between activated charcoal filter and

air filter using a hose clamp -3094- .

– Disconnect breather line -arrow- to solenoid valve in engine

compartment.

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in illustration.

– Connect valve adapter of tester -V.A.G 1371- to tyre valve.
– Regulate the pressure to 35 mbar with valve -A-. When the

pressure has stabilised, it must not drop below 30 mbar after

5 minutes.

If no pressure builds up or the pressure is not held for at least 5

minutes, localise leak as follows:
– Perform visual check on all components and hoses of the fuel

system.

Note

Also check fuel tank cap for leaks.

Only if still no fault has been detected:

– Check breather line and activated charcoal filter for leaks. To

do this, disconnect breather line -A- from activated charcoal

filter and seal connection with a plug -B-.

– Repeat pressure test.
If pressure still drops, the leakage can be found on the activated

charcoal filter or breather line:

– When valve is open -A-, check the following lines and compo‐

nents for leaks by hearing, touching, with commercially avail‐

able leak detector spray or using ultrasonic tester -V.A.G

1842- .

♦ Line from engine compartment to activated charcoal filter.
♦ Activated charcoal filter
If the pressure does not drop again, the leakage can be found on

fuel tank:

– To do this, reconnect breather line -A- to activated charcoal

filter.

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