Removing and installing high-pressure pipe: Audi A8 D4 (BUH, BUJ, CAJA, CAKA, …)

🧭 Before you start

Fits: Audi A8 D4 (4H, 2010–2017)

• Opens: fuel

Don't miss

• Risk of damage caused by particles of dirt.Observe rules for cleanliness . — Remove throttle valve module J338.
• The connections of the high-pressure pipe must not be damaged.Do not attempt to bend high-pressure pipe to a different shape.
• Tighten union nut with torque wrenchV.A.G 1331 and open-end spanner insert, 17 mmV.A.G 1331/8 or crow-foot ring spanner, 17 mm; to do so, counterhold at hexagon flats of threaded connection on fuel rail with an open-end spanner.
• Do not tighten bolt for retainer until high-pressure pipe has been tightened.

🔧 Engine codes this applies to

🔩 Torque settings

Values can differ between engine variants — check the code stamped on your block.

ℹ️ Always cross-check the exact figure against your vehicle's factory manual before final tightening — a wrong torque can damage the engine. These values are extracted from workshop data and may not cover every variant or revision.

📋 Procedure

1. Remove engine cover panel .
2. ⚠ The fuel system operates at extremely high pressure. This can cause injury.The fuel pressure in the high-pressure section of the injection system must be reduced to a residual pressure prior to opening the system . — Remove bolt (arrow) and detach bracket (1).
3. Release hose clips (arrows) and detach hoses.
4. Move clear vacuum pipe (1) and swivel to left side.
5. ⚠ Risk of damage caused by particles of dirt.Observe rules for cleanliness . — Remove throttle valve module J338.

6. Push down protective sleeve (1) and disconnect fuel line.
7. First press hose connector (2) downwards (arrow A), then press release tabs (arrow B).
8. Pull off hose connector, keeping release tabs depressed.
9. Release hose clip (3) and detach hose for activated charcoal filter.
10. Move clear hoses and push to left side.
11. Remove bolts (arrows) and push bracket (1) slightly to one side.
12. Remove nuts (arrows).
13. Remove union nuts (1 and 2) and detach high-pressure pipe (right-side).
14. Remove nuts (arrows).
15. Remove union nuts (1 and 2) and detach high-pressure pipe (left-side). [Note: The connections of the high-pressure pipe must not be damaged.Do not attempt to bend high-pressure pipe to a different shape.]
16. Tighten connection for high-pressure pipe to high-pressure pump .
17. First tighten union nut by hand until it makes contact, making sure that high-pressure pipe is not under tension.
18. Tighten union nut with torque wrenchV.A.G 1331 and open-end spanner insert, 17 mmV.A.G 1331/8 or crow-foot ring spanner, 17 mm; to do so, counterhold at hexagon flats of threaded connection on fuel rail with an open-end spanner.
19. Tighten union nut with torque wrenchV.A.G 1331 and flared ring spanner tool insert, 14 mmV.A.G 1331/8 or crow-foot ring spanner, 14 mm; to do so, counterhold at hexagon flats of threaded connection on fuel rail with an open-end spanner.
20. Do not tighten bolt for retainer until high-pressure pipe has been tightened.
21. Install throttle valve module J338.
22. Install engine cover panel .

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