BMW 7 Series: Conducting Leak Test On Fuel Tank And Tank Venting System

IMPORTANT: On vehicles with tank leak diagnosis modules (DMTL), do not work with external pressurization as the tank ventilation system will leak under this condition.

Observe country-specific accident prevention and occupational safety regulations.

NOTE: The following procedure is only applicable to vehicles with the tank leak diagnosis module (DMTL).

During the leak test with a leak detector, be sure to follow the operating instructions of the equipment manufacturer.

NOTE: Select "Tank leak diagnosis module (DMTL)" on Diagnosis and Information System (DIS).

• The leak diagnosis pump pressurizes the fuel tank and tank ventilation system for 30 sec.
• If pressure is needed for longer than 30 sec., press "Activate" button again after 30 sec.

The leak test can be carried out with a leak detector.

Possible causes may be:

• - Tank cap leaking (check TANK CAP PRESSURE RELIEF VALVE )
• - Tank ventilation lines leaky (fuel tank-activated carbon canister-tank ventilation valve)
• - Tank ventilation valve leaky (engine compartment)
• - Fuel level sensor flange on tank leaking

Fig. 5: Identifying Fuel Tank And Tank Venting System

DRAINING AND FILLING FUEL TANK

Notes

IMPORTANT: Observe country-specific safety regulations.

Do not damage non-return flap when pulling out extraction hose.

Diesel vehicles

Before starting the engine for the first time, if the tank has been run dry or drawn off, fill with diesel fuel and turn on ignition for approx. 1 minute. The fuel circuit is thus filled and vented, which results in the engine firing more quickly.

Drawing off fuel

Start engine and allow to run.

The electric fuel pump runs.

In this way, the fuel is repumped through the suction jet pump from the left to the right side of the fuel tank.

NOTE: Fuel can be drawn out of left and right sides of tank through filler neck, leaving only a small residue. The residual amount is drawn off via the service opening.

Insert special tool 16 1 080 into fuel filler neck.

Special tool 16 1 080 has two different diameters for petrol/gasoline and diesel vehicles! Slide extraction hose of extractor unit, refer to BMW Service Workshop Equipment and Planning Documentation, through special tool 16 1 080 into the fuel filler pipe, turning in the process if necessary.

Fig. 6: Inserting Special Tool (16 1 080) Into Filler Neck

Insertion length approx. 170 cm.

Draw off fuel with suction unit (refer to BMW Service Workshop Equipment) as far as possible.

Follow drawing off of fuel on fuel gauge in instrument cluster.

Drawing off residual fuel quantity

Drawing off residual fuel amount is not included in the time value of this operation.

IMPORTANT: Ensure car interior is adequately ventilated.

Catch dripping fuel in a suitable container.

Remove flange cover.

Draw off residual fuel quantity through service openings.

Fuel filling

Insert special tool 16 1 080 into fuel filler neck.

Special tool 16 1 080 has two different diameters for petrol/gasoline and diesel vehicles! Slide extraction hose of extractor unit, approx. 40 cm into fuel filler pipe.

Fill fuel from suction extractor unit.

Fig. 7: Inserting Special Tool (16 1 080) Into Filler Neck

Extracting fuel after a defect in the suction jet pump or fuel pump

Draw off right half of tank completely through fuel filler pipe.

Remove flange cover.

Insert extraction hose through service opening in tank, fuel (also residual quantity) can be drawn off.

FUNCTIONAL DESCRIPTION FOR GENERAL FUEL SUPPLY SYSTEMS

Fuel supply systems in gasoline engines

Fuel system

The fuel is delivered from the fuel tank by the fuel pump via the feed line with a defined primary pressure to the high pressure pump. The primary pressure is monitored by the fuel pressure sensor. The fuel is delivered by the fuel pump as required. A return line is not required.

Tank-venting system

The tank safety valve is a closed system that is bled via a carbon canister. The carbon in the canister is stored as granules. The large surface of the granules traps the fuel vapor, that occurs in the fuel tank. The carbon canister needs to be refreshed regularly in order to be able to continue to store fuel vapor. This is done by flushing it with fresh air from the intake pipe. This process is controlled by the engine control unit.

Diesel engine fuel supply systems

Fuel system

The fuel is delivered from the fuel tank by the fuel pump via the feed line to the high pressure pump. The fuel pump delivers more fuel than the engine requires. A return line is required.

Tank-venting system

Diesel fuel is slow-evaporating, therefore no carbon canister is required. The fuel tank is bled directly into the atmosphere.

OVERVIEW OF FUEL SUPPLY SYSTEM (PETROL/GASOLINE)

Fig. 8: Overview Of Fuel Supply System (Petrol/Gasoline)

1. Fuel tank
2. Tank fill level sensor
3. Flange cover
4. Fuel filter with pressure regulator
5. Fuel pump
6. Filling hose
7. Fuel filter pipe
8. Carbon canister
9. Tank leak diagnosis module (US version)
10. Dust filter (US version)
11. Carbon canister (US version)
12. Control unit for electric fuel pump
13. Fuel filter (outer)

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