Chevrolet Repair: Starter motor problems, chevy van g 20, starter motor problems

Question
I have a 92 chevy van,G 20,V-6 351 L.The starter motor only engages and turns the engine over for a secound and then disengages and spins.Some times it just spins and rarely it cranks it normally and starts.I've replaced the starter solenoid but there was now change.This problem started gradually over a period of a week and now I can be turning the key for 10 min. before it will turn over normally and start.
   Thank you for your time, David

Answer
Hi David,
Sorry this answer is so late...I signed out on vacation, but the site doesn't seem to update all the areas I am in, even though it says it will.
Actually, it sounds like corroded battery connections, a bad battery, or a missing ground cable from the engine to the firewall.
Take the battery cables off, and make sure where they contact inside those connectors is clean to bare, shiny metal.
You can remove the bolts, peel the red and black covers back off the rings, and use a wire brush and plain water to clean them.
Van