Function of the fuel tank ventilation - ra47006020030x(0030)

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Engines 602.96, 603.96/97 TURBO (Model 463.3: for deviations on cross country vehicles see introductory notes)

Fig 1: Identifying Fuel Tank Cap, Sealing Ring, Closing Bar And Compression Spring

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

All models

At a gauge pressure of 100-300 mbar, the fuel vaporization gases can escape through the cap. This is only the case, if e.g. the vent line from the fuel tank is not clear. If the system is operating properly, a gauge pressure of up to 50 mbar may occur in the fuel tank.

Fig 2: Identifying Vent System Components

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The vent system in the fuel tank (50) consists of a central pipe (54) each with an interruption vessel (54/1) at the ends. The interruption vessels prevent fuel escaping along the vent line.

The vent line (64) runs from the central pipe to the vent valve (51). The protective seal (51/1) at the end of the vent valve prevents dirt and splash water from getting into the vent valve.

If a gauge pressure of 30-50 mbar is reached in the fuel tank, the vent valve (4) opens and allows the fuel vapors to escape.

Fig 3: Vent Valve Function Diagram

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

If a vacuum of 1-16 mbar is produced in the fuel tank, the air admission valve (6) opens.

Station wagons

These models are fitted with a modified vent valve with a bright base section. The test data are the same as for other vent valves.

Fig 4: Vent Valve Function Diagram

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The dirt seal at the end of the vent valve prevents dirt and splash water from getting into the vent valve.

Fig 5: [Identifying Dirt Seal At End Of Vent Valve]

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Modified vent system

The vent system has been modified by additional lines and interruption vessels (arrows) with the result that no fuel can escape through the vent system, even under extreme conditions (rollover).

Production breakpoint: phased in (approx. 10/88).

Fig 6: Identifying Interruption Vessels And Central Pipe

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Model 201 plastic fuel tank

The plastic fuel tank is shaped in the top area (arrows) in such a way as to create the function of the vent system (central pipe).

Fig 7: Identifying Plastic Fuel Tank

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Model 140, as of Model Year 1992

Fig 8: Identifying Vent System Components

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

The vent system consists of a central pipe (54) with interrupt vessels (54/1) at the ends. The interrupt vessels (54/1) prevent fuel escaping along the vent line. The vent line (64) runs from the central pipe to the vent valve (51).