A capacitive discharge ignition system for an internal combustion engine and for use with a generator powered current source comprises a storage capacitor, at least one power thyristor for discharging the storage capacitor to transfer energy to at least one coil triggered in synchronism with an internal combustion engine with which the ignition system may be associated. A triggering circuit biases the power thyristor to discharge the storage capacitor. A shut-off circuit comprises a solid state device for switching the output of the generator to ground interrupting the flow of current to the power thyristor. A circuit sensing current flow in the triggering circuit generates a control and gates the solid state device into conduction in response to the control signal.