Basic principles of the activated charcoal canister
Here you will find useful basic information and important tips relating to the activated charcoal canister in vehicles.
Important safety note
The following technical information and practical tips have been compiled by HELLA in order to provide professional support to vehicle workshops in their day-to-day work. The information provided on this website is intended for use by suitably qualified personnel only.
Ever since the introduction of lambda control on vehicles with a catalytic converter, all emissions from a vehicle have been subject to legal regulations.
This also includes evaporating fuels (hydrocarbons) from the fuel tank. Since these so-called volatile hydrocarbons are not allowed to enter the atmosphere, they need to be captured and stored for reuse. In order to comply with legal regulations, retention and recirculation systems for fuel vapors are used here.
One important component in this system is the activated charcoal canister.
The activated charcoal canister is connected to the tank bleeder via the pressure compensation line and is used to capture and store fuel that evaporates under the influence of heat.
The timed valve is located in the connecting pipe between the intake pipe and activated charcoal canister. As soon as the lambda control is active, the timed valve is actuated and the line between the suction pipe and activated charcoal canister is released. As a result of the vacuum in the suction pipe, ambient air is sucked in through an opening in the activated charcoal canister. The air that is sucked in flows through the activated charcoal and guides the captured fuel to the engine for mixture formation.
Since the system affects the composition of the mixture, it only becomes active once the lambda control is operating.
Fault symptoms in the event of failure:
Causes of a failure: