Collecting Refuelling Gases

Collecting Refuelling Gases

129 With Engine 112 & 113
With Code (494a) USA Version
With Code (808) Model Year 1998
With Code (809) Model Year 1999
With Code (800) Model Year 2000

System Function:

Function Diagram Legend:

Task
- Legislation requires that the refueling vapors are recovered in the vehicle (ORVR = On-board Refueling Vapor Recovery).
- Separating fuel and refueling vapors so that no fuel is able to flow into the activated charcoal canister even if refueling is not carried out in the proper manner, or if the refueling pump nozzle is faulty.


NOTE: End the refueling operation when the nozzle shuts off and the fuel tank is full. On no account overfill the fuel tank by operating the nozzle again several times.


Function
The fuel vapors are recovered at the filler neck (45) and passed along a vent hose (a) to the activated charcoal canister. An insert in the filler neck prevents fuel flowing to the activated charcoal canister during refueling. The fuel vapors are deflected several times in the filler neck for this purpose in order to separate the vapors from the fuel. The connection to the activated charcoal canister is sealed off by means of a flap (45/1) when driving. It is opened by the nozzle when refueling.

Additional measures in the case of fuel tank being overfilled
- When the fuel tank is full, the float (45/2) with flap shuts off the filler neck at the bottom. As a result, the nozzle switches off more rapidly and overfilling is made more difficult.
- An excessive fuel level in the filler neck forces open the pressure relief valve (45/4). Fuel flows to atmosphere at the nozzle. End refueling!
This overfilling is not always detectable on nozzles fitted with rubber bellows (B).
- Excessive pressure in the ORVR vent line (a) acts on the diaphragm in the pressure relief valve (82). If the diaphragm lifts off because of excess pressure, the pressure is reduced at the fuel tank recess (e) and to atmosphere below the wheel housing (c). End refueling.
- If excess pressure exists in the activated charcoal canister (77), the pressure relief valve (77/1) opens. The pressure is released through the activated charcoal filter shutoff valve (Y58//4) to atmosphere (C).