Tap the side of the starter with the handle of a hammer. The brushes may be worn short and tapping will sometime move them enough to make contact. If that works replace the brushes. Have you checked the voltage at the starter. A volt meter or light bulb will do the trick. Check the voltage with the meter ground wire to a good ground and then to the starter body that should tell you about the starter ground. If the ground is not good at the starter check the ground strap on the engine block. Usually the back side of the starter will have an access to the brush an end of the armature. On mine there is a clamp screw that will allow you to slide a cover enough to see the inside. Give it a smell test if it is burnt it will smell burnt. The rebuild on the last dead starter at the local auto electric place wasn't much. The brushes are an easy fix that you can do.
good luck
Neil
