Take a screwdriver and jump the solenoid on the starter. The contacts inside the solenoid can corrode or simply wear out. If that doesn?t work, this is barbaric, I know, while the key is being turned to start tap the starter with a dead blow hammer. Sometimes the starter gets stuck in between the magnets. In my experience, if all parts are good, it?s a weak ground. Ground the motor and the starter with two different cables and make sure all of the contacts are clean.
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