91 Four Taurus keeps trying to start

Hello all. I have a 1991 Ford Taurus 3.0 V6 and when we go to start it, the thing tries to keep starting(turning over). Even after the key is turned off and removed. The starter just keeps going. Have to remove positive battery cable to stop it. While it was doing that the neg wire started to smoke. If I just touch the battery cable back on it tries to start. If it sits for a bit we can hook it back up and it works ok. I just had the starter and the starter solenoid replaced. Just wondering if anyone had any ideas as to what has possessed this thing. Thanks for any ideas advice.

I repaired a 1990 Escort that had the same problem. But, this one was a manual transmission so it would stop when the clutch pedal was raised. The problem was traced to the ignition switch (not the lock cylinder but the contactor on the other side). It had plastic plungers to hold contacts apart. The start plunger had melted and no longer held the contacts apart. Changing the actual switch part cured the problem.

Next time try switching into gear with the service brake “on” and see if the cranking stops.

Hope this helps.

Pull the starter relay to see if that stops the starting. If it is still starting, the starter solenoid may be at fault - usually that’s part of the starter and means that the starter has to be replaced.
If it stops starting with the starter relay pulled. whatever is driving that relay is always on. It could be the ignition switch, a pinched wire, etc.

My bet is that it is the starter - maybe the relay - but at least one of those two parts that were replaced. They may have replaced the starter with a rebuilt one that had your problem as an intermittent problem.

It could be a failing ignition switch; the electrical part. The root cause could be an aged cabin blower motor.
An aged blower will draw a lot more current than a good motor and over time that excess current will overheat the switch and cause it to fail. Sometimes one can even see the plastic starting to wrinkle or even melt.

The engineers routed the blower motor current through the switch instead of running it through a relay. That means that high current draw is being pulled directly through the switch. Not a very good idea on their part.
I went through 2 switches on my old Sable before sorting this out and decided to add a relay into the system. The switch was then used only as a trigger for the relay and the amount of current required for that is very miniscule.

Add to the list of possible causes the fender mounted solenoid.

Rod Knox,
Absolutely dead right. On my 87 I used to bang on that to get the car to start. LOL. If that bad boy is corroded either stuck open or closed is equally likely.