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.
RZV Ignition System
The Siemens MS42.0 system uses a multiple spark ignition function. The purpose of multiple ignition is:
- Provide clean burning during engine start up and while idling (reducing emissions).
- This function helps to keep the spark plugs clean for longer service life (new BMW longlife plugs).
Multiple ignition is active up to an engine speed of approximately 1350 RPM (varied with engine temperature) and up to 20 degrees after TDC.
Multiple ignition is dependent on battery voltage. When the voltage is low, the primary current is also lower and a longer period of time is required to build up the magnetic field in the coil(s).
- Low battery voltage = less multiple ignitions
- High battery voltage = more multiple ignitions
The 240 ohm shunt resistor is still used on the MS42.0 system for detecting secondary ignition faults and diagnostic purposes.
NO RELATED
Use the Manual With the Right Hardware
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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.