Fuel Pressure and Residual Pressure, Checking, A5 With TFSI Engine From MY 2012, A4 With TFSI Engine From MY 2013

Fuel Pressure and Residual Pressure, Checking, A5 with TFSI Engine from MY 2012, A4 with TFSI Engine from MY 2013

Special tools, testers and auxiliary items required

• Pressure Tester (VAS 6550) with Hoses (VAS 6550/1) and (VAS 6550/2)

• Vehicle Diagnostic Tester

• Measuring container, fuel-resistant

Procedure






- Open the fuel filler door.

- Remove the fuel filler cap - arrow -.

- Follow all test requirements. Refer to => [ Test Conditions ] Initial Inspection and Diagnostic Overview.








There is a risk of injury because the fuel is under high pressure.

• To reduce pressure in fuel system, lay a clean cloth around the connector and carefully loosen connector.

- Remove the fuel supply line from the retainer.

- Pull the release button to disconnect the fuel supply line - 1 -.

• Ignore - arrows -.

- Connect the (VAS 6550) and (VAS 6550/2) to the fuel supply line.






- Connect the (VAS 6550/1) and hold it inside a fuel resistant container.








Risk of fuel leak.

• Make sure that the drain - C - is closed.

• The level is perpendicular to the direction of flow.

- Open the shut-off valves - A and B -.

• The levers point in the direction of flow.

- Connect the tester.

- Turn on the ignition and select the following menu items on the vehicle diagnosis tester :

• OBD

• Engine Electronics

• Basic Setting

• Empty Fuel Tank

- Press Start: The fuel pump starts.

- If the fuel flows without bubbles, close the drain - B -, so that the fuel pressure increases.

• The level is perpendicular to the direction of flow.

- Read the fuel pressure on the (VAS 6550) :

• Specified value: 5.0 to 8.0 bar (72 to 116 psi).

- Press the Stop button.

If the specification is not attained:

- Check the fuel delivery quantity for the fuel pump. Refer to => [ Fuel Delivery Rate, Checking, A5 with TFSI Engine from MY 2012, A4 with TFSI Engine from MY 2013 ] Fuel Delivery Rate, Checking, A5 With TFSI Engine From MY 2012, A4 With TFSI Engine From MY 2013.

Checking Holding Pressure

- Watch the pressure fall on the (VAS 6550) while checking the holding pressure and checking for leaks:

• After 10 minutes there must be a residual pressure of at least 3 bar.

If the holding pressure drops below 3 bar:

• Check the connection between the (VAS 6550) and the fuel supply line for leaks.

• Check (VAS 6550) for leaks.

• Check fuel lines and their connections for leaks.

If no faults are detected:

• Replace the locking flange with the fuel filter and fuel pressure regulator. Refer to => [ Fuel Delivery ] Fuel Delivery.

- Repeat the residual pressure check.

If there are still leaks:

• There is a leak at the check valve in the fuel pump: Replace the fuel delivery unit, refer to => [ Fuel Delivery ] Fuel Delivery.

Assemble in reverse order of disassembling. Note the following:

• The ignition must be off.

• Open the shut-off valve - B - and drain valve - C - and let the fuel drain into the measuring container before to removing the pressure gauge for the fuel pressure.






- Remove the (VAS 6550) with hoses (VAS 6550/1) and (VAS 6550/2).

- Attach the fuel line so that it clicks into place.

- Press the fuel line on again and pull to make sure the connection is engaged correctly.