The car is a 1990 760 turbo.

The starter runs continuosly, even with the key to the "off" position -- even with the key OUT of the ignition, far as that goes. I had to disconnect the battery to get the starter motor to stop spinning. Doing this didn't reset anything -- the starter motor still spins when I reconnect the battery cable.

Prior to this, occasionally the starter drive would kick out of the flywheel prematurely on an occasional basis -- say about once out of every 20 times I started the car. I dunno if it's related to this issue, but I just thought I'd mention it.

When this problem occurred, the starter cranked the motor over as it always does, then the drive kicked out (before the motor caught), and the starter kept running.

Coincidently, an old motorcycle I own developed a starter problem also today (seems like I have starter karma right now), and looking through it's manual, I found a troubleshooting comment that listed the starter relay as being a possible culprit if the starter continues to run. So, I'm wondering if this sounds plausible?

Is there a way to test the circuit such that I can isolate the problem, be it the starter solenoid or the relay?

Thanks in advance for any help you can provide.

Best,
Michael