Electrical problem
1981 Other BMW Models 6 cyl Two Wheel Drive Automatic 360K miles
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Car is a 1981- 733i sedan with 3210 cm motor.
From handbook Electrical system is Digital motor electronics (Motronic) (uses L- jetronic fuel injection and transistorized coil ignition)
Parked car after full service (included tappet adjustment / resetting). Odessy battery with issolation switch fitted and used. Left for about a month then it would not start. No spark at spark plug. DME relay (Bosch) replaced but still no spark. Any idea what could be checked before towing car 40 miles to service centre?

check for power when key is on at the coil. This sounds like a loose wire issue. The early motronic is very robust and I would spend some time with it before sending it to someone who may or may not know the older cars as well as us olde timers.

Dr Hagerty, thank you for your response. The problem turned out to be the failure of the Reference mark sensor that reacts to the pin that protrudes from the flywheel ring gear. Regards Peter1

good eye Peter, keep in touch and happy holidays mate