General notes

Never start repair work on the fuel system without allowing the engine to cool down first. The coolant temperature must not exceed 40 °C. Compliance with this instruction is absolutely vital, as otherwise residual pressure within the high-pressure fuel system could result in uncontrolled fuel spray.

Special attention should always be devoted to maintaining clean conditions and to carefully following the repair instructions during all repair work. Even minute contamination and minor damage to the threaded connections on the high-pressure lines can result in leaks. Remove the ignition coils before installing the solenoid-controlled fuel injectors.

When carrying out repair work on the N55 always ensure that the ignition coils are not contaminated by fuel. Contact with fuel substantially reduces the ability of silicone to provide effective sealing. The result would be arcing between the spark plugs and the cylinder head, leading to ignition miss. Prior to working on the fuel system always remove the spark plugs and seal off the spark plug wells with shop towels to protect them from fuel.