Often when I start my car, hot or cold, it sounds like the solenoid is not engaging the starter. It's that spinning starter sound, it's sounds strong but like it's not making contact with the fly wheel. I had a guy Schuck's (Someday I'll learn not take their advice) tell be there wasn't enough juice to engage the magnet in the starter so it was just spinning but not extending to make contact with the fly wheel. I bought that long enough to buy the $30- solar battery charger to ensure that I had all the juice I needed whenever I start my car so I wouln't have to here that again. I do know that I have a short soewhere in the electrical system since my battery dies after about 3 days of sitting and I'm feeling too lazy to track down the short. Anyway, so now I've got this chargeing, the alternator checked out fine but the starter still makes the spinning noise. any ideas?
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1987 240 dl wagon 'rustbucket'

The starter solenoid actuates the bendix (pushes it into the flywheel) at the same time it makes electrical contact for the starter motor. In other words, one can't happen without the other. The spinning that you describe sounds like a defective starter bendix.