Fuel is extremely flammable, so take extra precautions when working on any part of the fuel system. Do not smoke or allow open flames or lamps without shades near the work area. Also, do not work in a garage with natural gas equipment with a wick. Always wear safety goggles and have a fire extinguisher ready for any work on the fuel system. If fuel comes into contact with skin, wash immediately with soap and water.
Before servicing the fuel lines, be sure to disconnect the negative cable from the battery and (on models with fuel injection) relieve pressure in the supply system (see Section Relieving pressure in the fuel injection system).
Fuel supply and return lines, as well as fuel vapor removal lines run from the fuel tank to the engine compartment of the vehicle. The lines are attached to the bottom of the car with clamps and screw assemblies. From time to time, the lines should be checked for dents, twists and other defects. Don't forget to also pay attention to the condition of the short sections of hose inserted into the main fuel line - they are the most likely source of leaks (see illustration).
If there are signs of dirt entering the fuel system or fuel filter, disconnect and purge the fuel lines. On models with fuel injection, also check the condition of the strainer on the submersible fuel pump.
Since the fuel lines on fuel injected models are constantly under high pressure, they are subject to special requirements. When replacing rigid pipes, use only genuine BMW pipes. Never install plastic or copper sections - these materials are not capable of withstanding the loads associated with high pressures.