Does it make an audible click? Have u replaced the celenoid on the firewall?

 

Yes one my trucks the one F-150 and the ranger there was click but no i haven't

 

If your truck has the fender solenoid, check the ground for that solenoid. I had the exact same issue with a 94 f150, and it took days of searching to finally find the culprit. Follow the ground from the solenoid to where it grounds (mine was on the fender). Mine was corroded and making sporadic connection.

 

Try the celenoid its cheap and can cause it

 

Well, for the sake of anyone else who has problems with an older model F-150 and searches out this thread, I think I discovered the problem. Someone else mentioned, I believe on another thread, that their starter would not disengage. After replacing my starter when the previous one quit working a few weeks ago, I noticed the new starter occasionally would keep grinding even after the engine started. I shut off the engine and the starter was still going. I turned the key and restarted the engine, and the starter disengaged. It happened again a few days later with my wife in the truck with me. She said, "That's the sound I heard the other day when the starter went out." I know it would seem obvious if the starter was still grinding, but, once the engine kicks in, it's not as loud as you might expect, and if the radio's going it would be easy to not really notice it.
I'm guessing that's what has happened before. So, if your starter just quits working - you turn the key and nothing happens. After you've eliminated the usual suggestions - like battery, ground wires, shift lever position, etc - when you replace your starter, listen closely when you start your truck. If the starter doesn't disengage, shut off the engine and restart it. It will probably disengage. If you drive it with the starter engaged, the starter won't survive the trip.