RZV Ignition System
Siemens MS42.0 system uses a multiple spark ignition function known as RZV ignition. The purpose of multiple ignition is to 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. 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 voltage is low, primary current is also lower and a longer period of time is required to build up magnetic field in coil(s). Low battery voltage equals less multiple ignitions. High battery voltage equals more multiple ignitions. A 240-ohm shunt resistor is used on MS42.0 system for detecting secondary ignition faults and diagnostic purposes. See Fig 1.