Before Opening High Pressure Fuel Injection System

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.

The fuel injection system is separated into a high-pressure section (max. approximately 120 bar) and a low-pressure section (approximately 6 bar).
Before opening high pressure area, fuel pressure must be reduced to a residual pressure of approximately 6 bar. The procedure for this is as follows.

Special tools and workshop equipment required

Vehicle Diagnostic Tester

Procedure

Fig 1: Checking DTC Memory With VAS 5051

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Proceed as follows:

-- ConnectVehicle Diagnostic Tester.

Display on Vehicle Diagnostic Tester:

Fig 2: Display On VAS 5051B - Vehicle Self-Diagnosis Button

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-- Start the engine and let it run in idle.

-- Press the OBD button -1-.

Display on Vehicle Diagnostic Tester:

Fig 3: Display On VAS 5051 - "01 - Engine Electronics"

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-- In selection -1-, press the "01 - Engine electronics" vehicle system and continue by pressing the → button.

Display on Vehicle Diagnostic Tester:

Fig 4: Display On VAS 5051 - "006 - Basic Setting"

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-- Press "measured values" listed in the menu -1- and then press the → button to continue.

Display on Vehicle Diagnostic Tester:

Fig 5: Display On VAS 5051 - "Display Group 140"

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-- In button field -1-, press buttons 1 4 and 0 "display group 140" and press the Q button to confirm.

Display on Vehicle Diagnostic Tester:

Fig 6: Display On VAS 5051 - (42%, 39.76 Bar, 40.63 Bar, Inactive)

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-- Check read-out for fuel pressure in fuel rail in display field -3-.

Example:

3 - 40.63 bar

-- Disconnect electrical connector -arrow- on Fuel Metering Valve -N290- on lower left high pressure pump at rear of engine.

Fig 7: Locating Fuel Metering Valve -N290-

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NOTE:

To provide a better illustration, component location is shown from behind with engine removed.

Display on Vehicle Diagnostic Tester:

Fig 8: Display On VAS 5051 - (42%, 39.76 Bar, 40.63 Bar, Inactive)

Courtesy of AUDI OF AMERICA, LLC

-- Check read-out in display field -3- :

Fuel pressure in fuel rail must sink to approximately 6 bar.

-- Turn off the ignition.

The fuel rail will continue to be filled with fuel, but it will no longer be under high pressure.

WARNING:

Do not let fuel come into contact with skin.

Wear protective eyewear and clothing when opening the fuel system.
Lay clean cloths around the connection before opening the high pressure area to collect any fuel that leaks out.

-- Loosen the wire at a connection immediately.

NOTE:

If the high pressure system is not opened immediately, the pressure will increase because of post-heating.

Final procedures

-- Re-connect electrical connectors.

Faults are saved in ECM when electrical connectors are disconnected:

-- Vehicle Diagnostic Tester Connect.

-- Start "Guided Functions " operating mode.

-- Generate readiness code in ECM.