Fuel Supply Line: Service and Repair

13 53 334 Removing and installing/replacing pressure line (N53, N54, N54T)

Special tools required:







WARNING:
Observe warning on cylinder head cover.
Disconnect negative battery terminal (risk of fire due to short-circuiting on removal).
Electric fuel pump starts up automatically each time door is opened.
Carry out installation work on fuel system only with coolant temperature below 40 °C.







IMPORTANT:
Wear full face guard and protective gloves.
Fuel can emerge spontaneously at high speed when the high pressure line is released.







IMPORTANT: Adhere to conditions of absolute cleanliness when working on the high-pressure fuel system.

Introduced contaminants can cause malfunctions in the system.
- Do not allow any dirt particles or foreign bodies to get into the system.
- Remove all traces of dirt contamination before removing lines or separate components.
- Use only fluff-free cloths.
- Seal all fuel system openings with protective caps or plugs.
- High pressure lines may be re-screwed a maximum of 10 times.







IMPORTANT:
Ignition coils must not be contaminated by fuel.
The resistance of the silicone material is reduced significantly by contact with fuel, which may cause the ignition coil to fail.
Cover ignition coil with suitable means.







Necessary preliminary tasks:
- Remove intake plenum.







Recycling:
Fuel escapes when fuel lines are detached.
Catch and dispose of escaping fuel in a suitable container.
Observe country-specific waste disposal regulations.







Release nuts (1 and 2).
Release screw (3).
Disconnect high pressure line (4).
Seal connections of high pressure line (4) with matching plugs from set of special tools 32 1 270.







Seal fuel line connection of high pressure pump (1) and high pressure rail with matching plugs from set of special tools 32 1 270.







Installing pressure line:
Installation of pressure line is described separately from removal.
Copper seals that may be fitted (1) are no longer needed and must be removed.
If reusing the pressure line, apply a light coating of transmission oil to threads of pressure connections. New pressure lines are already coated.







Install pressure line (4).
In so doing, tighten screw connections (1 to 3) hand-tight only.

IMPORTANT:
Install pressure line (4) without tension only.
To ensure distortion-free installation of the pressure line and to avoid damaging the thread, it must be possible for both nuts (1 and 2) to be screwed on easily by hand.
If the nuts cannot be screwed on easily by hand, the high pressure pump must be slackened.
This operation is described in the following section.







Only if high pressure pump has to be slackened:
Slacken screws with special tool 11 8 610.
Turn high pressure pump (1) on flange so that nuts of high pressure line can be easily screwed on by hand.
Tighten down screws. Tightening torque 13 51 1AZ.







IMPORTANT:
Follow sequence of screw connections:
1. Tighten down nut (1) with special tool 13 5 020. Tightening torque 13 53 7AZ.
2. Tighten nut (2). Tightening torque 13 53 7AZ.
3. Tighten down screw (3) for holder. Tightening torque 13 53 2AZ.







Assemble engine.
Check fuel system for tightness.
Check function of DME.