Fuel Pump: Description and Operation

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 Faulty Suction Jet Pump

Tow-in due to faulty suction jet pump.

• If suction jet pump is faulty, the vehicle can stop running due to lack of fuel, though the fuel tank is up to 1/4 filled.

If the suction jet pump does not function, up to 15 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 the vehicle stops running, although the fuel tank is approximately 1/4 filled, proceed as follows:

- Check fuel pump. Refer to => [ Fuel Pump Electrical, Checking ] Fuel Pump Electrical, Checking.

If the fuel pump is OK, but no fuel is supplied:

- Fill fuel tank with approximately 5 liters of fuel.

- Start the engine.

If the engine starts now:

- Replace suction jet pump. Refer to => [ Suction Jet Pump ] Suction Jet Pump.