a failed regulator/rectifier will not cause loss of spark unless something is internally shorted in the stator which means it is defective and must be replaced.

Does a voltage regulator control spark?

The regulator/ rectifier is a voltage regulator that keeps the battery supplied with a steady 13.4 dc volts no matter what the stator is putting out, which is AC volts that varies with engine RPM. A bad regulator/ rectifier will result in a dead battery, and once the battery is competely dead you will not get a spark.

What are the symptoms of a bad voltage regulator?

A bad voltage regulator can even affect your car's engine. For example, as this car part stops working properly, you might notice your car's engine sputters or stalls once in a while. It might also have trouble accelerating as you drive.