Suction Jet Pump, Checking

WARNING: This page is about a different car, the 2015 Audi A3. However, it is still accessible from the selected car via links, so may be relevant.

On vehicles with All Wheel Drive (AWD) the fuel tank is divided into a left and a 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.

Fig 1: Identifying Suction Jet Pump Function

Courtesy of AUDI OF AMERICA, LLC

Function of suction jet pump

The suction jet pump functions according to a simple physics principle: A suction jet from the electric fuel pump is pushed through 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:

Tow-in due to faulty suction jet pump.

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 15 liters of fuel (up to approximately ¹ /₄ tank) remain in left chamber of fuel tank, because it cannot be extracted by the fuel delivery unit.

If vehicle stops running, although the fuel tank is approximately ¹ /₄ filled, proceed as follows:

-- Fuel pump, checking in Guided Fault Finding . Refer to Vehicle Diagnostic Tester.

If the fuel pump is OK but no fuel is carried:

-- Fill approximately 5 liters of fuel.

-- Start the engine.

If The Engine Now Starts:

-- Replace the suction jet pump. Refer to SUCTION JET PUMP, REMOVING AND INSTALLING .