Gas evaporative control system (EVAP)

Since 1970 Volvo vehicles intended for the markets USA and CAN are fitted with a gas evaporative control system (EVAP). This prevents gas fumes from being released into the atmosphere.

The system consists of an expansion canister and a venting filter, which is filled with active carbon. Also included are the connection hoses between the various components.

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The venting filter (early production) is located behind the radiator grille.
1 Connection to inlet duct  2 Connection from expansion container  3 Attaching screw

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The expansion container is placed to the left in the luggage compartment, next to the filler pipe.
1 Connection from tank  2 Connection from filler tube  3 Connection to venting filter

EVAP principle

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Venting Filter: 1 Foam plastic filter  2 Active carbon  3 Felt  4 Wire gauze  5 Perforated Plate  6 Container  7 Connection to inlet duct  8 Connection from expansion container

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EVAP principle: 1 Fuel tank  2 Expansion container  3 Inlet duct  4 Venting filter

Gas fumes forming in the hermetically sealed container, particularly during warm weather, are conveyed to the expansion container (2) and from there to the venting filter (4) where they are mixed with the active carbon.

When the engine starts, air is drawn through the venting filter and into the engine via the inlet duct. Gas fumes stored in the active carbon are drawn by the air flow into the engine where they take part in the combustion.

The foam plastic filter for the evaporative control system should be changed every 25,000 miles (40,000 km). The foam plastic filter is fitted on the bottom side of the canister. To replace, slacken the screw (3) and lift up the venting filter.