Right in the center, under the large B-M-W plate on top of the motor. Only the M42 engine has a distributor cap, The M50 engine has no spark plug wires as the coils sit directly on top of the spark plugs
step by step:
Check the cap and rotor for signs of burning, carbon tracks or excessive corrosion on the terminals. Do not try to clean the terminals. The cap and rotor should be replaced at the same time.
1:Make sure the ignition is OFF.
2:to prevent scraping the skin off your knuckles on the radiator fins, slide a thin piece of cardboard or equivalent down between the radiator and the fan.
3:Remove the ignition lead cover from the distributor cap. If not already marked, tag the ignition leads for later installation.
4ull off the ignition leads from the distributor cap.
5:Remove the screws from the distributor cap and remove the cap. Check the condition of the distributor cap seal and replace if necessary.
6:Unscrew the 3mm hexhead bolts holding the rotor and remove the rotor.
To install:
7: Place the new rotor on the shaft and tighten the hexhead bolts to 1.9-2.1 ft. lbs. (2.6-3.0 Nm).
8: Replace the distributor cap and seal. Tighten the mounting screws.
9: Replace the ignition leads on the proper terminals and clip the cover into place. Remove the cardboard from between the radiator and fan.