I like Deejay’s fuel pump switch but not so sure about the small fuse with the isolator!
If the car is a Duratec and unless you have fitted one yourself I don’t think it will have an alarm so you would only be powering the immobiliser and keeping the ecu memory alive. IMO the learnt data is not worth much. It’s mainly only the fuel trims and they are soon relearnt. I don’t think you would notice much difference. I swop ecu’s in and out quite often and don’t really notice anything. As for keeping the immobiliser powered on I don’t think that adds much value from a security perspective as it would activate as soon as the car was powered anyway. Regarding isolation when working on the car a small fuse may help prevent a fire but wouldn’t necessarily prevent damage from say an accidental reverse polarity mishap.
Good luck!
