On-Board Refueling Vapor Recovery Function - GF47.10-S-3004TRC

Engine 274 in model 447, 448 

Courtesy of MERCEDES-BENZ USA

On-board refueling vapor recovery, general points 

The lawmaker requires that the refueling gases are captured in the vehicle.

Fuel and refueling vapors must be separated in order to prevent fuel from flowing into the activated charcoal canister (1) even when there is inappropriate refueling or a defective nozzle.

Function sequence for on-board refueling vapor recovery 

The filler neck (2) is so molded that the fuel is accelerated out of the nozzle in the filler neck (2) and therefore the air is suctioned around the nozzle into the fuel tank (3).

As a result of this air intake. the refueling vapors are not able to gather at the filler neck (2) and are able to escape.

The fuel vapors flow through the aeration/vent valves (4) and aeration/vent lines (5) to the activated charcoal canister (1), where they are stored.

If fuel gets into aeration/vent valves (4), the aeration/vent lines (5) are closed off, thus preventing fuel from flowing into the activated charcoal canister (1).

The aeration/vent valves (4) can also close briefly if there is sudden braking or acceleration, or when cornering.

For an opened purging switchover valve (Y58/7) the fueling gases are suctioned together with the fuel gases from the activated charcoal canister (1) over the purge line (6) by the engine and burnt.