1987 ford f150 keeps starting itself....

What's happening is that you are getting defective solenoids. It can happen. Finding a 'good' aftermarket one is almost impossible. All of them are made in China now. Just keep taking them back until you get one that works, or try a different supplier, and maybe you will get a different brand. Let us know, please, as I am hoping to buy a 1980 Colony Park, and it uses the same solenoid, and I have almost given up finding a good one to replace a defective old one. Not sure quite what to do if I need one again.

I'm a little confused: The solenoid smokes and fails even though you aren't using the starter? The only time that the solenoid carries a load is when the starter is engaged. Granted - all of your main electrical source is on one post of the solenoid, the other should be un-powered unless you're attempting to start the engine. I have an '87 F-250 4x4 - I have never had a solenoid problem (in fact, In my 30+ years as a Ford tech - I have rarely ever seen a solenoid fail on its own) I've had an ignition switch (electrical) that came apart and did all kinds of weird stuff but it's likely that you have something else going on - causing the overload on the solenoid.

Tracy, I have had exactly what the OP has described, and it was a solenoid problem every time. I have also had solenoids fall apart, quite literally, and quite spontaneously. It is very possible for them to stick on, or not to open quite all the way and get a spark jump inside, and that will cause them to smoke, and they can catch fire that way, too.

thanks guys, any information can help, im really frustrated!

Actually your solenoid is fine but you have an extra wire connected to it somewhere. It causes it to be a ghost truck. Check the wiring system and see what's connected and what shouldn't be. The wrong wire will be somewhere towards the bottom left near the solenoid.

might be your ignition switch,check if the power from the ignition wire to the solenoid cuts of once its starts.

Not only would a defective solenoid cause this problem, but the Ignition Switch will also do exactly the samething. I have two 85 F150s and I replaced the questionable solenoid with the solenoid that I knew was good. When that did not fix the problem the Ignition Switch was the next part to replace. I have not had any problems since.