Fuel Tank: Description and Operation

GF47.10-P-2000MIR Component Description For Fuel Tank
- MODEL 230.454 with ENGINE 272.949 as of Model Year 09 /AEJ 08 model refinement package
- MODEL 230.458 with ENGINE 272.968 as of Model Year 09 /AEJ 08 model refinement package
- MODEL 230.471 with ENGINE 273.965 as of Model Year 09 /AEJ 08 model refinement package





Fuel tank shown, except code (494) USA version
45 Fuel filler neck
55 Fuel feed module with suction jet pump
55/1 Fuel filter with integrated fuel pressure regulator
75 Fuel tank
76 Vent valve
B4 Fuel level sensor
M3 Fuel pump
A Fuel to fuel manifold
B Aeration and venting of the fuel tank

Location
The fuel tank is located in the trunk above the rear axle.

Design
The fuel tank has a filling capacity of about 80 liters, and is made of sheet steel.

When the fuel tank is full, a float with flap closes off the fuel filler neck. This ensures that the refueling nozzle shuts off more rapidly and overfilling is largely prevented.

At the top of the fuel tank is a fuel level indicator sensor for detecting the fuel level.

The swirl pot contains a suction jet pump, which fills the swirl pot with fuel when the fuel level is low.
While cornering when the fuel level is low, the swirl pot prevents the fuel pump from drawing in air.

A coarse filter is installed in the feed line to the fuel pump.

Function
Fuel feed
The fuel pump draws fuel from the bottom of the fuel feed module and pumps it through the fuel filter with integrated fuel pressure regulator to the fuel distribution rail (one-line system). The fuel pressure is limited to about 3.8 bar by the fuel pressure regulator.

The fuel return from the fuel pressure regulator drives the suction jet pump, which is used to fill the swirl pot when the fuel level is low.

Emptying
The fuel tank has no outlet valves. It is emptied by the related air extractor system.

Aeration and ventilation, except code (494) USA version
The fuel tank is aerated/vented through the vent valve, the aeration/ vent line and the activated charcoal canister.

Ventilation
The vent valve opens at an overpressure of about 30 to 50 mbar in the fuel tank, and the fuel vapors flow through the aeration/vent line to the activated charcoal canister.

Air admission
The air admission valve opens when there is a vacuum of ca. 1 to 16 mbar in the fuel tank and air or fuel vapors are suctioned over the activated charcoal canister.

Refueling
The vent valve opening pressure of about 30 to 50 mbar is not reached when the tank cap is removed. The vent line to the activated charcoal canister remains closed off. This means that the nozzle switches off quicker.

Aeration and ventilation with code (494) USA version
The fuel vapors flow through the two safety valves (rollover valves) placed at the top, and through the aeration/vent pipe and the aeration/vent line to the activated charcoal canister.

The safety valves close off the ventilation system if there is an accident, thus preventing fuel from flowing into the activated charcoal canister.