You can see this when the ECU is bad. Spark at initial on and at off. Also just ran into this with a car that would only start as the switch was released. It was a butchered up repair, but some one had spliced a new connector to the distributor and wired it reverse. So we had a repeatable ignition spark only at on and off (once). Once we reversed the plug, the car would fire in the start position.

The ECU is looking for a negative pulse to fire the coil, which it gets when ignition is turned off. Since coil is already charged and capacitors in ECU have voltage you can see this response.

If you have voltage at the resistor and at the coil in run and start position, your bulkhead connector is OK. If you did not mess with distributor you should try swapping the ECU.