1978 BMW 633CSi Automatic TransFACTORY OEM SERVICE PROCEDURE

BOSCH Electronic Ignition: Operation

Inside the distributor, a trigger wheel turns with distributor shaft. The trigger wheel has one tooth or lug for each engine cylinder. As trigger wheel rotates past lugs of magnetic pick-up coil, a magnetic field is built up that continually builds and collapses. This produces a low voltage electrical signal.

This signal passes to the electronic control module, which controls dwell angle and at the same time interrupts ignition coil's primary current. This induces high secondary coil output voltage that fires spark plugs.

Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • β€’ You smell fuel, burning insulation, or see smoke.
  • β€’ Brakes feel soft, pull hard to one side, or make grinding noises.
  • β€’ The engine overheats, stalls repeatedly, or misfires under load.
  • β€’ You are missing required tools, torque specs, or safe lifting equipment.
  • β€’ You are not confident in the next step or safety outcome.

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