Brief description
| Brief description |
All hydrocarbons that evaporate while refuelling must be dealt with by the car and not emitted to the surroundings. Max. 0.2 g hydrocarbon/gallon fuel is allowed to leak out while refuelling 15-38 litres (4-10 gallons) fuel/min. It should be possible to fill the tank at 15-38 litres (4-10 gallons) fuel/min up to 95% of the total capacity without the pump nozzle shutting off prematurely so that topping up is required.
A leak corresponding to a hole larger than 1mm (0.040”) in diameter must be detected by the fuel evaporation system.
System description
Fuel is filled through the fuel filler pipe and passes through the check valve down to the tank. The fuel filler pipe acts as an ejector. Fuel flowing down into the tank is accompanied by air from outside and prevents fuel vapour from being emitted to the surroundings via the opening in the fuel filler pipe. The fuel being filled forces the gaseous hydrocarbons and the air being drawn down into the tank through the float valve into the EVAP emission canister. The hydrocarbons are absorbed in the emission canister and the air is let out through the shut-off valve.At a certain level (approx. 95%), the float valve shuts and the pressure in the tank increases. The fuel now rises in the filler pipe and shuts off the pump nozzle when it reaches it. The check valve in the filler pipe prevents ”back-spit” when the nozzle is shut off.
The positive pressure remaining in the tank passes slowly through the roll-over valve in the emission canister. As the positive pressure in the tank drops, the fuel will be emptied from the filler pipe.
When the engine starts, the emission canister is gradually purged by air being drawn into it via the shut-off valve. Hydrocarbon/air mixture passes through the EVAP canister purge valve into the engine and is ignited.
From M01, there are three different emission requirements:
1. OBD II LEV for US/CA. Has full ORVR with tank integrity diagnosis, fuel vapour recycling and CHECK ENGINE on in the event of an emission-related diagnostic trouble code.
2. E-OBD, EC2000 for EU/NO/CH. Has reduced ORVR with fuel vapour recycling but no tank integrity diagnosis, which means that cars with this variant do not have a shut-off valve or tank pressure sensor. The CHECK ENGINE lamp comes on only in a few cases.
3. L-OBD for other markets. L-OBD is identical to E-OBD with the exception that L-OBD does not turn on the CHECK ENGINE lamp in the event of emission-related diagnostic trouble codes.
In cars with full ORVR and ORVR without tank integrity diagnosis, the EVAP canister is located on top of the tank. In cars without fuel vapour recycling, it is under the front right wing.
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B205E
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B235E
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B235R
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B308E
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Filler pipe
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Without vapour recycling
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X
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X
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With vapour recycling. Without EVAP diagnosis
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X
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X
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With vapour recycling and EVAP diagnosis
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X
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X
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X
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Fuel tank
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Without vapour recycling
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X
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X
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With vapour recycling. Without EVAP diagnosis
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X
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X
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With vapour recycling and EVAP diagnosis
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X
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X
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X
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EVAP canister
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Without vapour recycling
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X
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X
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With vapour recycling
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X
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X
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X
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