I have a 1991 Ford explorer that I having a problem with. I have narrowed it down to the fuse control panel on the left side of the engine compartment.
It will drain the battery if let sit for a couple of days without starting, short time when its cold. I'm getting an arch of the both battery post when I take them on and off which tells me there is a drain somewhere. If I take the fuse out of the emmission contol slot on the panel it does not drain. I replace it and its starts right off. Its a hugh pain to do this day after day tho.
Do you have a manual with a circuit diagram. How about the owners manual. Ou need to check what components the fuse protects and look at each individually. I would look for a bare wire shorting on one of the compomemets.