Checking the operation and replacing fuel injectors (BMW 5 Series E28)

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 unshaded lamps near the work area. Do not work in garages with natural gas equipment with a wick (types of water heaters and clothes dryers). If fuel comes into contact with your skin, wash it off immediately with soap and water. Wear safety glasses and keep a fire extinguisher handy when working on the fuel system.

Examination

Check on the car

1. Using a mechanical stethoscope (available at most auto supply stores) check for clicks in each injector when the engine is idling (see illustration).

If you don't have a mechanical stethoscope, you can check the clicks in the injectors with a screwdriver. Place the end of the screwdriver on the injector and press the handle to your ear.

2. When operating, the injectors create a steady clicking sound.

3. Increase engine speed above 3500 rpm. The clicking frequency should increase with engine speed.

4. If the injector does not function (no clicks), buy a special lamp for checking injectors from an auto accessories store and connect it to the electrical connector of the injector. Start the engine and check the resistance that the lamp blinks. This means that the injector is receiving the correct voltage, so the injector itself is faulty.



5. Disconnect the connector of each injector and check the resistance of the injectors. Compare the results with those given in Table of sizes and adjustment data at the end of the Manual with the values. Replace all injectors with the wrong resistance value.

Checking the volume

Since injector volume testing requires a special injector tester, this procedure is beyond the capabilities of a home workshop. Have your BMW dealer or other specialist perform the injector volume testing.

Replacement

1. Disconnect the main electrical connector of the fuel injectors cable. Remove the intake manifold (see Honor Repair work carried out without removing the engine from the vehicle).



2. Disconnect the fuel hoses from the fuel line and unscrew the fuel line mounting bolts (shown by arrows).

3. Remove the fuel line/injectors assembly from the intake manifold.

4. Installation is the reverse of removal. Remember to replace all O-rings. To prevent damage to the rings during installation, lubricate them with a thin layer of engine oil. Create pressure in the fuel system (install the fuel pump fuse and turn on the ignition) and check for leaks before starting the engine.