Had the exact same problem twice with two different issues at hand. First was the shifter coming loose and it wouldnt go all the way into park hence it not starting, it would just click. Up under the dash i found the place it was missing a bolt and luckliy i had kept the bolt that hit my foot one day while driving down the road. hahaha.

Second was the large wire connecting the starter solenoid to the starter motor and that SOB left me stranded one day, thank god for roadside assistance. 257 dollars is what they charged my insurance company. hahaha. Those are two off the wall issues but very likely. The wire in this Picture shows how it had corroded through. That poor old engine was such a mess, see hands!

If you attempt the jump with a screw driver make sure to get heavy duty rubber gloves, preferably yellow ones, a traffic cone on your head to channel energy, and a 20'X60' tarp to contain the mess when you explode! haha sorry i couldnt help it. a guy did that to me but used realistic "things i would need" and had me going for a second. Damn old ford techs with a sense of humor. It will work just fine to start it if you have the key on but just to test, key off, slightly touch the two posts with a screwdriver and you will know if it is working. Problem with the whole mess on that is when i did that test, it didnt work so i thought it was the fender solenoid for sure. So i had my spare out and replaced it just to find out that with the new one it didnt do **** either. Check the starter connections. trust me