[RallySnake]

Mike,

I would use a 30 amp relay (depending on the current draw of the pump motor) and wire it to the ignition switch. This would work most of the time. If you had a low battery, it could make starting the car difficult, though.

You might want to wire it through a separate switch. You could turn this on after the engine was started, but it is very important that you not forget.

You know, I would go to the electronics store and buy a time delay relay. I would wire it to the ignition switch so that it would come on one minute after the engine is started. This would give a cold engine a minute to generate some heat and start recharging the battery. A hot engine could run for a minute without a problem, too. The nice thing about this solution is that you don't have to think about it, it just works.

If you need help wirng this circuit, let me know. It would help to know the current requirements of your pump. (Amps or Watts)

Paul