Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1981 BMW 633CSi Automatic TransFACTORY OEM SERVICE PROCEDURE
Ignition Coil Resistance Check
- Turn ignition switch "OFF". Using an ohmmeter set at the low scale, attach leads to ignition coil primary terminals 1 and 15 (wires removed). See Fig 1. Take primary resistance reading.
- On Mercedes-Benz models, the coil has a pressure relief plug located on top of the coil. Make sure the plug has not popped out. If it has popped out, replace coil.
- Set ohmmeter to x1000 scale, then connect ohmmeter leads to negative terminal 1 and coil tower terminal 4 (high tension). Take secondary resistance reading. If either the primary or the secondary reading was not within specifications, replace coil.Ignition Coil Resistance Specification
Application Primary Secondary BMW .4 Fiat Strada & X1/9 1.1-1.7 6000-10, 000 Mercedes-Benz .7 8000-11, 000 Porsch .33-.46 7000-12, 000 Saab 1.05-1.35 5500-8500 Volvo 1.0-2.0
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.