So today I decided to change my battery cables with my new nos Ford cables on my 92 4.0. It was not easy but got it done. I had to remove the starter and cut a piece off the old positive wire a splice a male spade connector to so I could plug it in the new positive cable to the starter. So I started and everything was fine. Ran a few errands and then when I left the store I was at the engine started but it was still cranking so I didn't know what to do. I even took the key out it still was cranking. It quit doing it after about a minute. Then I started it back and it did fine. What could have happened just changing my cables? What can I do if this happens again so it won't burn my starter or catch fire?

 

Seeing as how you didn't mention having this problem before removing the starter during the battery cable replacement, revisit All of the wire connections on the starter, to make sure the solenoid connections are tight & positioned such that they can't make contact to cause the bendix solenoid accidently activate & make the starter motor continue to run.
If the connections check out ok & this is just happenstance, maybe the solenoid contacts welded when the starter was engaged for the start??? Those are about the only scenarios I can think of that would cause the starter motor to continue running after the ignition was turned off & the key was removed.
The B+ post on the starter is always hot, so if the solenoid that operates the bendix to engage the engine flywheel & crank the engine had its high amp electrical contacts weld/stick closed on a start, the starter motor won't turn off after we go to run, or off on the ignition switch to open the solenoid electrical connection, to have the bendix spring retract the flywheel drive & break the starter motor high amp B+ contacts. Those contacts pull mucho amps on a cold start, so can sometimes over heat & sitck/weld closed, causing the kind of situation you had.
If it happens again, be prepared to jump out & thump the starter solenoid & starter motor with a sizeable piece of wood, to see if you can jar it enough to loosen the stuck contacts.
Or, if all else fails, disconnect the B- cable, but disconnecting the B- cable at the battery can be dangerous with the starter motor running, as it'll arc & spark Plenty bad from the starter high current demand, so be sure to wear at least safety glasses, gloves, face shield, long sleeves, ect, in case the battery explodes from the sparks igniting hydrogen gas given off by the discharging battery. All that is better than risking a fire from the starter motor continuing to run, or battery cable insulation, or battery overheating & catching fire.
If it does it again & the thump works, replace the starter solenoid contacts, or starter motor assy, or run it by a reman shop to have them do it.
Some thoughts for pondering, let us know what you find.

 

Is the starter motor relay another possible culprit? Maybe the cable running down to the starter solenoid was reconnected in a way that its connector is allowing conductance into the relay's other terminal? From my limited experience a faulty starter motor relay can also cause the starter to continue operating after the key is removed.

 

When I installed the new cables I tried to route them like originally but that bracket on the pass side block was hard to work with but I got the cable routed through one of those looms. The starter has a wire bolted to the small stud and it was spliced to the old positive cable. My new cable had a flat female connector for the starter. So I cut the old splice off added a male flat connector and plugged it into my new positive cable so I didn't have to ruin it. It's been ok since last night hope it stays this way. I'm going to check the starter connections today and replace the fender relay. Can't I just unplug that push in connector on the relay if it happens again? Oh yeah all the starters I look at have the stud connector instead of the male flat terminal.