Setting the ignition timing of a contactless system (BMW 3 Series E21)

Connect the "+" clamp of the stroboscope to the "+" terminal of the battery, the "ground" clamp to an unpainted part of the body, and connect the clamp of the stroboscope sensor to the high-voltage wire of the 1st cylinder.

Disconnect the vacuum hoses from the ignition distributor and run the engine at idle speed.

Direct the flashing beam of the strobe light into the clutch housing hatch. When the ignition timing is set correctly, the mark on the flywheel should be in the center of the hatch.

To adjust the ignition timing, stop the engine, loosen the ignition distributor flange mounting bolt and turn it to the required angle.

Start the engine and check the ignition timing again.

Repeat the above steps until the correct ignition timing is set.

Check the ignition timing in dynamics (see subsection "Detailed technical specifications".

Tighten the ignition distributor flange mounting bolt and connect the vacuum hoses to it.

[Information taken from this resource: BMWMAN.RU]