Abstract: A detection system for determining spark voltage of a spark plug in a capacitive discharge ignition system is disclosed. The detection system may have a sensor circuit configured to detect occurrence of a spark by measuring a voltage on a low side of a primary coil. The detection system may also have an electronic control unit connected to the sensor circuit. The electronic control unit may be configured to receive a signal from the sensor circuit indicating that the voltage exceeded a threshold. The electronic control unit may be further configured to determine a spark time based on the signal, and determine a spark voltage based on the spark time.