Fuel Delivery and Air Induction: Description and Operation
Vehicles with All Wheel Drive as of 11.2004
=> [ Fuel Tank, Draining ]
=> [ Suction Jet Pump ]
Fuel Tank, Draining
Special tools, testers and auxiliary items required
• Wrench (T10202)
• Fuel Extracting Device (VAS 5190)
Procedure
Observe safety precautions. Refer to => [ Safety Precautions ] Fuel Supply System.
Observe rules for cleanliness. Refer to => [ Clean Working Conditions ] Fuel Supply System.
CAUTION!
• Observe safety precautions when disconnecting the battery.
All except Audi RS4:
- Push the cover over the battery toward the right - arrow 1 - and remove it upward - arrow 2 -.
- With ignition switched off, disconnect Battery Ground (GND) cable - arrow -.
Audi RS4:
- Raise luggage compartment floor covering and secure.
- With ignition switched off, disconnect Battery Ground (GND) cable - arrow -.
All:
CAUTION!
Secure the Fuel Extracting Device (VAS 5190 ) Ground (GND) wire to a bare area of the chassis.
- Remove the cone piece - 2 - from the shaft piece - 1 - on the Fuel Extracting Device (VAS 5190 ).
- Using insulating tape, apply a mark - arrow - on hose at length - a - = 1,865 mm from end of suction hose.
- Remove fuel filler cap from fuel filler tube.
- Install the shaft piece - 1 - for the Fuel Extracting Device (VAS 5190) on the fuel tank filler tube.
- Push the suction hose as far into fuel tank until the mark applied earlier - arrow - is positioned on shaft piece.
• If using a siphoning device without shaft piece, proceed principally in the same manner.
• In this case, apply a mark - arrow - using insulating tape on hose at length - a - = 1,800 mm from end of suction hose. The suction hose is inserted correctly when the marking applied earlier stands opposite the lip of fuel filler tube.
• If the hose can only be inserted with difficulty, coat it thinly with engine oil. Never use lubricants containing silicon.
- Drain fuel tank through fuel filler tube as much as possible.
- Carefully pull out the suction hose.
- Remove rear seat bench.
- Remove cover for right locking flange - arrows -.
Audi RS4:
- Free up electrical connector - arrow - for Fuel Pump (FP) Control Module (J538) and disconnect.
All:
- Disconnect electrical harness connector - arrow - at right locking flange.
- Mark the fuel return line - 1 - and fuel supply line - 2 -.
CAUTION!
Fuel system is under pressure! Before opening system, place clean rags around the connection. Then release pressure by carefully loosening the connection.
- Pull both lines from locking flange, by pressing the release buttons.
- Remove locking ring with Wrench (T10202).
- Pull locking flange and sealing ring from opening of fuel tank.
- Slide suction hose, a dimension of - x - = 800 mm in length, through right opening of fuel tank into left fuel tank chamber.
- Empty left fuel tank chamber.
- Install right locking flange again => [ Installing ] Service and Repair, observing notes for connecting battery.
Suction Jet Pump
The fuel tank in a vehicle with all-wheel drive is divided into a left and right chamber. To move the volume of fuel from the left fuel tank chamber - 3 - to the right baffle housing of the fuel delivery unit - 2 -, a suction jet pump - 1 - is utilized.
Function of suction jet pump
Function of the suction jet pump is based on a simple physical principle: A suction jet from the electrical fuel pump is compressed by a nozzle in the suction jet pump and is thereby accelerated. This acceleration causes the surrounding fuel to be drawn in and be forced to the baffle housing of the fuel delivery unit.
Malfunctions of defective suction jet pump
CAUTION!
If suction jet pump is defective, the vehicle can stop running due to lack of fuel, though the fuel tank is up to 1/4 filled.
If suction jet pump does not function, up to 20 liters of fuel (up to approximately 1/4 tank) remain in left chamber of fuel tank, because it can not be extracted by the fuel delivery unit.
If vehicle stops running, although the fuel tank is approximately 1/4 filled, proceed as follows:
- Check fuel pump. Refer to => [ Fuel Pump, Testing Electrically ] Vehicles With All Wheel Drive as of 11.2004.
If the fuel pump is OK, but no fuel is supplied:
- Fill fuel tank with approximately 5 liters of fuel.
- Start engine.
If the engine starts now:
- Replace suction jet pump. Refer to => [ Suction Jet Pump ] Service and Repair.