I have a 91 F150 straight 6 manual trans, I have replaced the starter(Advanced auto) , replaced the solenid(OEM) by the wheel well, disconected the ignition switch at the column and still it stays engaged causing the truck to attempt to run and crank simultaniously causing the battery to die. when attemping to jump the battery the starter is still engaged. When this initially occurred I had drove it approx 20 mins (running wonderfully), ran into store back out 5 min tops! couldnt start it came back in the morning started fine, a couple weeks and a few parts later same thing! now it wont de-energize the solenoid? any ideas? thanks for your time in advance.

 

something is wrong at the starter relay.

1. it may be stuck closed do to a high amperage draw and the contacts arced together.

2. wired incorrect. battery cable should be on 1 big post with a few other wires and the starter wire on the other by itself.

3. the small signal wire is telling the relay to close. either shorted to another 12v source or ignition switch is bad.

use a multimeter or test light to test the small signal wire. should only have 12v when trying to start it. if no voltage, (or you can disconnect it) then there should not be continuity between the 2 big posts. first make sure its wired correct.

 

I am happy to report that your advise was dead on! I had just replaced the solenoid but do to a defective(new) starter the relay contacts were welded together. I went and got a new starter and solenoid. problem solved!!! thanks again for your PROMPT reply it was most appreciated!!!