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
P47.30-2332-79
Schematic diagram of fuel tank aeration and ventilation |
1 | Fueling, pressure limitation and bleed valve | 5 | Purge control valve | 8 | Ventilation valve and bleed valve | ||
2 | Aeration and ventilation valve | 6 | Dashpot | A | Ventilation and bleed line | ||
3 | Filler neck | 7 | Activated charcoal canister | B | Purge line | ||
4 | Fuel tank |
Owing to its shape, the filler neck for the fuel tank functions as a suction jet pump. The fuel flowing out of the pump nozzle accelerates the available air in the filler neck during refueling. This results in differential pressure, which causes the fuel vapors that formed around the pump nozzle to also be sucked into the fuel tank. The release of fuel vapors is therefore minimized.
The fuel vapors flow through the vent and bleed valves and the lines to the activated charcoal canister, where they are stored and later supplied for combustion.
The fueling, pressure limitation and vent valve also prevents overfilling by closing off the aeration and vent line.
During heavy braking, accelerating, or cornering, the vent and bleed valves of the fuel tank can be closed off for a short time. This prevents fuel from entering into the purge line via the vent and bleed valves.