FOX 2004 ➤
3 - Cyl. injection engine - Edition 12.2009
lk
2
Activated charcoal filter system
Operation ⇒ page 80 .
Activated charcoal filter system components - repair
⇒ page 81 .
Check fuel compartment ventilation ⇒ page 81 .
2.1
Operation
Fuel vapours form over the fuel surface on the tank, depending
on the atmospheric pressure and ambient temperature.
The activated charcoal filter prevents these hydrocarbon emis‐
sions from being released into the atmosphere.
The fuel vapours coming from the highest point of the tank go
through the gravity valve (which closes at a 45° inclination) and
check valve, strangled in its amount, to the activated charcoal
filter.
The activated charcoal absorbs these vapours like a sponge.
While driving and with Lambda adjustment active (hot engine),
the electromagnetic valve 1 for activated charcoal filter system -
N80- , (also known as regeneration valve) is activated cyclically
by the Engine control unit -J623- , due to engine speed and load.
The opening period depends on the input signals.
Intake manifold vacuum aspirates fresh air through the vent open‐
ing on the lower part of the activated charcoal filter, during the
activated charcoal regeneration process. The fuel vapours stored
in the activated charcoal and the fresh air are fed for combustion
in dosed quantities.
The pressure retention valve prevents the fuel vapours from being
aspirated into the fuel reservoir, when the Magnetic valve I for
activated charcoal filter -N80- is opened and there is vacuum in
the intake manifold. This way, the activated charcoal filter regen‐
eration is ensured.
With no current (e.g., driver interruption) the Magnetic valve 1 for
activated charcoal filter -N80- remains closed. The activated char‐
coal filter will not be purged.
Note
♦ The flexible tube joints are fixed with a quick coupling.
♦ Always replace fastening clamps with spring clamps.
♦ To install spring clamps, we recommend using the Standart-
type clamp pliers -VW 5162 - or Standart-type clamp pliers -
VAS 5024A- .
Follow safety measures ⇒ page 65 .
Follow cleaning rules ⇒ page 65 .
80
Rep. Gr.20 - Supply system - tank, Fuel pump (pre-supply pump) G6
English 
