Fuel Pressure Test

WARNING: This page is about a different car, the 2010 Audi Q7, 2009 Audi Q7, 2008 Audi Q7, and 2007 Audi Q7. However, it is still accessible from the selected car via links, so may be relevant.

Special tools and workshop equipment required

Multimeter.
Fuel Line Adapter Set VAG 1318 / 17A. These tools may be substituted with an equivalent aftermarket tool and are also available for rental or purchase through Audi.
In- line fuel pressure gauge with shutoff valve (high pressure).

Test conditions

Battery voltage 12.5 V.
Function and voltage supply for the Fuel Pump is OK.
Fuel tank at least ¹ /₄ filled.
Ignition switched off.

Test procedure

-- Perform a preliminary check to verify the customers complaint. Refer to PRELIMINARY CHECK .

WARNING:

Fuel system is under pressure! Before opening the system, place rags around the connection area. Then release the pressure by carefully loosening the connection.

Start diagnosis

-- Disconnect the fuel supply line at the supply location and catch any fuel coming out with a shop towel.

NOTE:

Pull circlip upward to unlock fuel line.

-- Install a fuel pressure gauge with appropriate adapters.

-- Open shut off valve on fuel gauge.

-- Switch ignition on and off repeatedly until fuel pressure stops increasing pressure.

-- Read fuel pressure on the gauge.

Specified value: 3.5 - 6 bar.

If specification is exceeded:

-- Check return line between the fuel filter and the fuel pump for kinks or blockage.

If no malfunction in fuel return line is found:

-- Pressure relief valve in fuel filter is malfunctioning.

-- Replace the fuel filter. Refer to appropriate repair information.

If reading was below the specification:

-- Check fuel pressure at the fuel filter between the fuel pump and the fuel filter using appropriate adapters.

-- Open shut off valve on gauge and start the engine. Allow to idle.

-- Slowly close the pressure gauge, shut off and note the fuel pressure.

Pressure must increase to 6 bar.

When 6 bar is reached: Open shut off tap immediately!

If pressure has increased during test:

-- Fuel pump is OK. Pressure relief valve in fuel filter is malfunctioning.

-- Replace the fuel filter. Refer to appropriate repair information.

If pressure did not increase:

-- Fuel pump is faulty

-- Replace the fuel pump. Refer to appropriate repair information.

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

Check the DTC memory. Refer to DIAGNOSTIC MODE 03 - READ DTC MEMORY .
If necessary, erase the DTC memory. Refer to DIAGNOSTIC MODE 04 - ERASE DTC MEMORY .
If the DTC memory was erased, generate readiness code. Refer to READINESS CODE .