I'll have a remote water pump on the Duster and I'm trying to figure out the best way to wire it. I can wire it to the ACC circuit so it is on whenever the ignition key is on or in ACC. That would allow me to run it with the engine off if I wanted to cool the engine down.

I can wire it to IGN on so it is on when the key is on or the engine is on.

I can also use the EFI system to control it. For instance, I can program the ECU to turn the pump on whenever the engine is running (speed over 500 rpm). If I do it that way then it is a little more fool proof, but I can't turn it on with the engine off.

Does the water pump need to be run when the engine is off? Only reason I can think of is to help cool the engine down between rounds.