Hopefully your injection pump was not damaged because of this. I hope your regulator and return line were able to reduce the line pressure enough as not to cause any damage. Even on reduced speed, I would be inclined to think that would be a lot of pump- at the very least, a lot of return fuel from the regulator back to the tank. That 42402 pump is A LOT of pump. It's the biggest high pressure pump we offer.
The input to the center terminal on the pump is what determines what it does. If the center terminal sees nothing or voltage, it goes into full speed mode. If it sees ground, it goes into reduced speed mode.