I have a 1966 Mustang when I charged the battery because it had sat for a while it turned over twice and then nothing, I changed solenoid, ignition switch, and key barrel still nothing. I can start it from the solenoid but when I try to turn it off it won't shut off. Won't start from key or shut off from key...Please help

That's because your talking about the starter relay on the fender right! It's N/G when you turn on the key your jumping one side to the other which is the cable from the battery to the cable going to the starter that is bad inside the connection should end when you turn the key to the off position but it's not so the engine keeps running and possibly the starter is still cranking if not your lucky because that's what usually happens and it kills the starter and chews up the flywheel now did this happen before you changed any parts or after if after the ignition switch you changed is not adjusted properly so when you turn the key to the off position the circuit isn't opening and killing the voltage you see I have no idea when you did what so this is also a possibility look at the starter motor there is a braided strap at the end the nose of the starter in the front it's a ground strap if it's frayed and broken all you will get is a click when you turn the key also you changed the ignition key switch this is connected to the ignition switch by a rod that goes down the column and if you didn't connect it well nothings happening and if you did connect it I'm certain that you didn't adjust the ignition switch not the key switch you have to leave the screws or nuts loose a little bit and move the switch around back N forth to get it right so it starts and shuts off when it's supposed to I'm trying real hard to help you so you really need to be specific about how and when you changed things before or after and write down the order of things you are doing and still doing otherwise anyone here who picks up on you can help remember none of us are at the vehicle with you so you ar e the eyes and ears that tells us what your doing or have done so post back a little more precisely if this has not helped you already good luck and make sure all connections are clean Never use a wire brush it ripps the metal to shreds and on lead cable terminals the result is loose cables 4 0// that's 0000 grade steel wool is what you use to clean terminals eyelets on cables and wd40-pb blaster liquid wrench and a carbon conductive grease to lube them NEVER USE THE SPRAY IT TURNS THE WHOLE AREA LIVE AND MORE PROBLEMS LIKE SHORTING TO GROUND AND FIRES can result and in case your wondering I'm a taxi mechanic with 50 years experience in nyc and your info is good stuff good luck again I have to go back to an alternator rebuild and transmission install on a crown victoria the chariot drivers here are amazing they drive through store windows at least once a month and if you ever come here walk the streets facing the cars so you can see it before your a hendrix lyric tire tracks all across your back I see you had your fun! And have fun fixing your girl mustang Sally yay stephen