What does it mean when the starter motor spins freely?

[JuniperMarie]

Causes of a starter motor spinning freely: 1. The shift fork of a mechanical forced starter is disengaged, unable to push the drive pinion or improperly adjusted in travel, preventing engagement. 2. The plunger stroke of an electromagnetic control starter is too short. 3. The auxiliary coil of a moving-armature starter is short-circuited or open-circuited, failing to bring the armature to the working position. 4. The starter one-way clutch slips. 5. Severe wear or damage to the flywheel teeth. Here is some relevant information: During engine starting, the starter draws 344 to 400 ampere-hours from the battery. To prevent overcurrent or damage to the battery, the starting duration should not exceed 5 seconds. In winter, when starting difficulties are common, multiple starting attempts should avoid prolonged durations, with appropriate intervals between each attempt.