GF47.30-P-3013L Fuel Evaporation Control System, Function
GF47.30-P-3013L Fuel Evaporation Control System, Function
The fuel evaporation control system prevents fuel vapors escaping to atmosphere. This is done by storing the fuel vapors temporarily in the activated charcoal canister.
When the engine is running, the fuel vapors stored in the activated charcoal canister are drawn off through the purge control valve and combusted in the engine.
The activated charcoal canister is purged (re-generated) at:
- Coolant temperature > 70 degrees C
- Blocking time after engine start elapsed, approx. 2 minutes
- Engine not in deceleration mode
The purge quantity is controlled by the ME-SFI control unit operating the purge control valve. The purge quantity is determined by constantly opening and closing the purge control valve for on and off periods of various lengths.
The idle speed control prevents changes in engine speed resulting from purging. A richer or leaner fuel-air mixture is produced in line with the charge of the activated charcoal canister with fuel vapors.
Air admission to fuel tank
Air is admitted through the activated charcoal canister. This is done through the activated charcoal canister, whereby air is drawn out of the vent/breather line or fuel vapors are drawn from the activated charcoal canister into the fuel tank.
Air release from fuel tank
The fuel tank is vented through the activated charcoal canister. The fuel vapors flow to the activated charcoal canister, where they are stored or drawn into the intake manifold in case of simultaneous regeneration.
Vent valve
On vehicles fitted with a vent valve the fuel tank is vented from a pressure of 30 to 50 mbar, and air admitted at a vacuum of 1 to 16 mbar. In addition, this prevents overfilling the fuel tank.
(USA) as of MY 98
During refueling the fuel vapors are collected at the filler neck and passed to the activated charcoal filter (ORVR=Onboard Refueling Vapor Recovery). Large activated charcoal canister.
Engines with charging (compressor or turbocharger)
A check valve in the purge line prevents the boost pressure building up toward the activated charcoal canister.
The additional vent valve (76/1) prevents the vacuum from the intake manifold passing over the activated charcoal canister through to the fuel tank for enabled purging. For this purpose, the valve closes as soon as a membrane is pressurized with vacuum pressure from the activated charcoal canister. If excess pressure or vacuum pressure affects the other valve connection, it opens immediately. This means aeration/venting of the fuel tank is then possible in an unlimited fashion via the standard vent valve (76).
Pay attention to the installation position of the vent valve (76/1). Check aeration at the activated charcoal canister for contamination (e.g. dust, spider's webs).