Collection Of Gases When Refueling, Basic Function - GF47.10-P-1002A

Engine 139, 176, 177, 254, 256, 260, 264, 274, 279, 282 

Overview 

This document contains information on:

• General 
• Function requirements 
• Function 

General 

Due to legally determined emissions limit values, it is necessary to collect fuel vapors because ecologically harmful emissions occur as a result of fuel vapors. The liquid fuel and fuel vapors must be separated during this process so that no fuel can enter the environment in the event of inappropriate refueling or a defective pump nozzle.

Function requirements 

• Engine management ON (circuit 87M)

Function 

Courtesy of MERCEDES-BENZ USA

Sample diagram of fuel tank ventilation 

Due to its shape, the filler neck (3) to the fuel tank (4) has been designed as the suction jet pump. The fuel flowing from the pump nozzle accelerates the available air in the filler neck (3) during refueling. This results in a differential pressure, which causes the fuel vapors that form around the pump nozzle to also be intaken into the fuel tank (4). The release of fuel vapors is therefore minimized.

The fuel vapors flow via the vent and bleed valves (2, 8) and lines to the activated charcoal canister (7), where they are stored and later supplied to the combustion.

In addition, the refueling, pressure limitation, and bleed valve (1) prevents overfilling by closing the vent and bleed line (A).

During heavy braking, acceleration, or cornering, the vent and bleed valves (2, 8) of the fuel tank (4) can be closed for a short time. This prevents fuel from entering the purge line (B) via the vent and bleed valves (2, 8).