Fuel Rail: Service and Repair
WM 243019 Removing and installing fuel distribution pipe (fuel rail) on DFI engines
Tools
Technical values
Preliminary work
1. Remove intake-air distributor. => 244619 Removing and installing intake-air distributor on DFI engines - section on "Removing"
Information
Component overview
Fuel distribution pipe
Removing fuel distribution pipe (fuel rail)
DANGER
Danger of poisoning from fuels.
-> Gasoline is toxic.
-> Inhaling vapours can cause irritation of the mucous membranes and eyes.
-> It can be carcinogenic. It represents a serious risk to health when inhaled, touched or swallowed over longer periods.
-> Only work on the fuel system in well-ventilated rooms.
-> Wear protective gloves that are fuel-resistant.
-> Wear a breathing mask with active charcoal filter; do not breathe in any fuel vapours.
-> Ensure that there is adequate ventilation and extract all fuel vapours.
-> Before opening the fuel lines or fuel hoses, relieve the fuel pressure.
-> Collect escaping fuel, absorb it if necessary with a suitable binding material and dispose of properly.
-> Pay attention to cleanliness when working on the fuel system.
DANGER
Danger of fire from fuel.
-> Keep clear of ignition sources.
-> Do not smoke.
-> Disconnect battery.
-> Danger of fire due to naked flames and sparks, e.g. during welding or grinding work.
-> Danger of fire due to escaping fuel, e.g. on hot engine components or due to electrostatic charge. Allow engine to cool down.
-> Secure the vehicle, e.g. with a warning sign.
-> Change any clothing soaked with fuel immediately.
-> In case of fire, use CO2 or dry powder fire extinguishers.
CAUTION
Dirt on injection system components (intake manifold injection and direct fuel injection system)
- Material damage
- Rough-running engine
- Bad exhaust emissions
-> Thoroughly clean connection points and adjacent areas before loosening them. If the engine is very dirty, wash it before starting disassembly work.
-> Lay removed parts on a clean surface and cover them. Do not use fibre-shedding cloths.
-> Carefully cover components or seal them if repair work will not be carried out immediately. Place rubber caps on connections. Seal intake openings with film or adhesive tape.
-> Only install clean parts. Do not take spare parts out of the packaging until just before installation.
-> Never use compressed air when the system is open. Do not move the vehicle.
CAUTION
Danger of fire from leaking high-pressure lines.
- Fuel can leak out if high-pressure lines are bent or damaged.
- Fuel can leak out if threaded joints are not fitted correctly.
- Fuel can leak out if the tightening specifications are not observed.
-> Never bend high-pressure lines.
-> The high-pressure distribution pipe (rail) or other fuel feed components in the high-pressure area must always be completely removed.
-> Perform a visual inspection to ensure that connection points are undamaged and perfectly clean.
-> Check that threaded joints at connection points are not seized up or corroded. Make sure the thread is not damaged.
-> Fit union nuts on all connection points by hand before screwing in screws or bolts.
-> Pay attention to cleanliness. Remove dirt on the ball/conical joints.
-> Check or inspect connection points for leaks following assembly.
Information
- The ignition must be switched off when working on the fuel system.
- Absorb any escaping fuel using a suitable binding material or a cloth.
- Cloths which have absorbed fuel must be disposed of according to the applicable national laws.
- The fuel system must be depressurised before starting work on it.
- Only work on the fuel system in well-ventilated rooms.
- Any seals which have been removed must always be replaced.
1. Pull off cable plug for high-pressure sensor. -2-
High-pressure fuel distribution
2. Place a cloth around the high-pressure connection on the high-pressure line -3-. Relieve the fuel pressure by slowly opening the high-pressure line with an open-ended wrench.
3. Loosen all eight union nuts for the high-pressure fuel injectors -1-. Use an open socket socket-wrench insert Nr.18-1 or similar tool to do this.
Socket
4. Remove screws on fuel distribution pipe (fuel rail) -1 and 2- and lift off fuel rail. The screw on the thermostat housing is longer. The rear right screw can only be reached using a thin Torx wrench.
Mount for fuel distribution pipe
5. Remove fuel rail from the engine by twisting it.
Fuel rail in engine
Installing fuel distribution pipe (fuel rail)
WARNING
Loose purge connection
- Emerging fuel
- Risk of fire
-> Check that the purge connection of the fuel distribution pipe is seated securely.
-> Tighten the purge connection of the fuel distribution pipe to the correct tightening torque.
Fuel distribution pipe
1. Using the leak test equipment, blow the fuel out of the high-pressure pump and the high-pressure line into a cloth. Shake the fuel distribution pipe over a cloth to remove fuel residues. => 243001 Checking fuel distribution pipe (fuel rail) on DFI engines for leaks
2. Fit fuel rail on the engine by twisting it. => Fuel rail in engine
Fuel rail in engine
Information
When fitting the union nuts, make sure that the connection taper of the high-pressure line is loose in the injector. It should be possible to screw on the union nut easily without greasing it and without the use of force (check that it is straight and screws on easily). Loosen the injector retainers and correct the positions of the various components if necessary.
3. Fit fuel rail.
High-pressure fuel distribution
3.1. Carefully lift up the coolant vent line at the rear if necessary and slide the fuel rail into installation position.
3.2. Screw fuel rail on loosely. Screw union nuts loosely onto the injectors. Only fit screws and union nuts loosely until everything fits. -1-
3.3. Also fit the high-pressure line -3- between the rail and high-pressure pump.
4. Fit screws on fuel distribution pipe (fuel rail) -1 and 2-. The screw on the thermostat housing is longer. The rear right screw can only be reached using a long, thin Torx wrench.
Mount for fuel distribution pipe
5. When all threaded joint positions fit correctly and without tension, tighten all threaded joints according to the prescribed tightening torques. The union nuts for the injectors and the high-pressure feed line must first be tightened initially, then loosened and then tightened finally. => Fuel line (high-pressure line) to injector (high-pressure fuel injector) (3 turns: tighten, loosen, tighten) => Initial tightening: 25 Nm (19 ftlb.) , then loosen, then => Final tightening: 25 Nm (19 ftlb.) ; fuel gallery (high-pressure rail) to crankcase => Tightening torque: 10 Nm (7.5 ftlb.) ; fuel gallery (high-pressure rail) and thermostat housing to crankcase=> Tightening torque: 10 Nm (7.5 ftlb.)
Use an open socket socket-wrench insert Nr.18-1 => Socket or similar tool to screw on the injectors. Fasten the high-pressure line with an open-ended socket ring wrench Nr.185 and a torque wrench.
Socket
6. Check the high-pressure system for leaks. => 243001 Checking fuel distribution pipe (fuel rail) on DFI engines for leaks
7. Connect cable plug for high-pressure sensor. -2-
High-pressure fuel distribution
Subsequent work
1. Fit intake-air distributor. => 244619 Removing and installing DFI intake-air distributor - section on "Installing"
2. Bleed the fuel high-pressure system. => 2430B1 Filling and bleeding the DFI fuel high-pressure system (includes bleeding fuel distribution pipe)