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

Engine 256.9 in model 213, 238, 257, 290 up to model year 2021 with code 494 (US version) 

Engine 256.9 in model 222 with code 494 (US version) 

Courtesy of MERCEDES-BENZ USA

Schematic illustration of fuel tank 

On-board refueling vapor recovery 

The legislator requires that the refueling vapors 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 (77) due to any inappropriate refueling or a defective nozzle.

Owing to its form, the filler neck (45) functions as a suction jet pump. As a result, the fuel coming from the pump nozzle accelerates in the filler neck (45), and the air around the pump nozzle is suctioned into the fuel tank (75). As a result of this air intake, the refueling vapors cannot rise up at the filler neck (45) and escape into the open air.

The fuel vapors flow through the aeration/vent valves (75/2) and aeration/vent lines and the aeration/vent lines (A) to the activated charcoal canister (77), where they are stored. By closing off the vent and bleed line (A), the refueling, pressure limitation, and bleed valve (75/1) additionally prevents overfilling. Rollover valves are integrated at the top of the aeration/vent valves (75/2). If fuel gets into aeration/vent valves (75/2), the aeration/vent lines to the activated charcoal canister (77) are closed off, thus preventing fuel from flowing into the activated charcoal canister (77). The vent and bleed valves (75/2) can also close briefly in the event of sharp braking, acceleration or cornering.

When purging is enabled, the refueling vapors are suctioned off by the engine together with the fuel vapors from the activated charcoal canister (77) via the purge line (B), and are burnt.