Fuel Pressure Test

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.

NOTE:

When the door is opened the fuel pump is activated for 2 seconds to build up the pressure in the fuel system.

Models with an airbag are installed with a fuel shut - off system. It reduces the danger of a fire in a crash as the fuel pump is switched off via the fuel pump relay.

Test procedure

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

WARNING:

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

Start diagnosis

-- Disconnect fuel supply line -3- at the supply location and catch any fuel coming out with a shop towel

Fig 1: Identifying Breather Line, Vacuum Line & Fuel Supply Line

Courtesy of AUDI OF AMERICA, LLC

NOTE:

Pull circle clip 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 to 6 bar

If specification is exceeded:

-- Check return line between fuel filter and 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 Service Information.

If reading was below the specification:

-- Check fuel pressure at the fuel filter between fuel pump and 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 Service Information.

If pressure did not increase:

-- Fuel pump is faulty

-- Replace the fuel pump. Refer to appropriate Service Information.

Final procedures

-- Reinstall the engine cover with air filter, if necessary. Refer to the appropriate Service Information.

-- 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 .