While you have the battery out have a good look at the connector on the starter post (loose, corroded etc.).
Attached is something to give you an idea of what the mechanical switch looks like.
Attachments
Starter Example 01.jpg (57.48 KB, 211 downloads)


"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."