On-Board Refueling Vapor Recovery Function - GF47.10-P-3004MNA

Engine 177.9 in model 205, 213, 253 

with code 494 (US version) 

Courtesy of MERCEDES-BENZ USA

Schematic diagram, model 205 with code 494 (USA version) up to model year 2016 

Courtesy of MERCEDES-BENZ USA

Schematic diagram, model 205 as of model year 2016 and 213 with code 494 (USA version) 

On-board refueling vapor recovery 

The law requires, that the refueling gases in the vehicle are collected (On-board Refueling Vapor Recovery). Fuel and refueling vapors must be separated in order to prevent fuel from flowing into the activated charcoal canister due to any inappropriate refueling or a defective nozzle.

The filler neck is designed so that the flow of fuel is accelerated during refueling and ambient air is sucked into the fuel tank. As a result of this air intake. The refueling vapor are not able to gather at the filler neck and are able to escape. The refueling vapor flows to the activated charcoal canister via aeration and vent valves and appropriate lines. This is where the vapor is stored. The fueling, pressure limitation and vent valve also prevents overfilling by closing off the aeration and vent line. Rollover valves are integrated at the top of the aeration/vent valves. If fuel gets into the aeration or vent valves, the rollover valves close the aeration and vent lines to the activated charcoal canister. Fuel cannot flow into the activated charcoal canister. The aeration/vent valves also close briefly in the event of heavy braking, acceleration or cornering.