weirdest starter problem ever, still a mystery.

I have an '87 F-250 with a 300-6 and a 4-speed. The starter has acted strangely, about 5 time since I have owned it, two of which were in the last week, so I must fix the problem sooner than later so I don't get stranded. Here is the problem...
I turn the key to start the engine as I always have (there aren't too many ways to mess up this step) and the starter motor races as if the bendix gear (pinion) did not engage with the flywheel. When I release the key from the start position, the starter motor continues to spin. I have each time completely removed the key from the ignition, and still had the starter spinning. Each time I have stopped its spinning by pulling my battery ground cable, which I religiously keep loose now.

I am pretty sure that the problem is not related to the starter switch because of two seperate reasons:
1 My radio and all of the accessories like the heater turn off when I remove the key.
2 The ignition switch malfunctioning and maintaining undesired current to the solenoid would not cause the starter motor itself to mechanically not engage properly.

Despite the fact that start and accessory are two 'seperate' circuits within the same ignition switch, I have ruled it out as the cause.

Occasionally (more frequently when the problem was new than now when the problem is chronic) the starter would not engage, and I would just release the key from the start position, allow the starter to stop spinning, and re-start the engine; which never was unsuccessful.

I have no clue at all what would cause two seemingly seperate problems to line up so perfectly (starter mechanically not engaging, and starter still spinning after key is removed). If anyone has had a simaler problem, let me know what the cause was, and I will promptly replace that part. Any ideas? Any information would be very helpful, because after 4 years as a mechanic, I have never seen this and don't even know what "this" is. Thanks. :screwy:

something wonky with the starter solenoid. Might want to check it out.

yeah I'd check the solenoid out, it should be mounted on the passenger side fender near the battery.

I have the same problem in my 88 4.9 4x4. Only my stater does engage and continues to spin the engine with the key off. Yes, I have to pull the battery cable.
Do you have an answer? I have changed the starter relay starter switch on the column, switch and wiring harness form the key to the junction under the column.
tgillcoke@yahoo.com

Usually when the starter stays engaged, the starter solenoid itself is at fault.

Ford switched from the old reliable field type starter (no solenoid) to a new smaller Perminant Magnet starter w/solenoid in the late '80s, and by now many older starters have been "upgraded" (really downgraded) to the newer style.

I would just replace the starter if it's of the newer type.