Anyone know what role the Solenoid plays in turning the starter over? My assumption is that the solenoid boosts the voltage going to the starter to engage the bendix by drawing power from the coil. Is this correct? The reason I ask this is because I am having issues of not being able to turn the starter over in my '66 Mustang. I have taken the starter casing off and can get it to turn over by manually engaging the bendix and using a battery charger as my source of power. Any ideas would be appreciated.

Thanks,

 

Well it sounds like the solenoid is bad. And/or the connections to the solenoid or its ground are corroded, dirty not making a connection. The base of the solenoid needs to be cleaned also, as it grounds the solenoid.
The solenoid is the actual switch that tells teh starter to start cranking. You can actually jump the terminals right on the solenoid, in essence bypassing it, and get it to crank that way.
Things to check: battery terminals - make sure they are clean and shiny. Battery and starter cables - make sure they are free of corrosion and clean. If they are corroded at all, ideally they should be replaced. Remove the solenoid and clean all of the connections and the base. Reassmble. That should take care of it. The solenoids rarely are truly bad, usually theyre not making a connection and most people replace em. Any time Ive ever had a trouble a ford that the solenoid isnt attached to the starter its always been that the connections were dirty as all hell, I would clean em and it would start right up.
-P.