When the starter spins but does not engage the flywheel What is wrong?

When the starter spins but does not engage the flywheel, it typically indicates a problem with the starter solenoid or the starter drive mechanism (often referred to as the Bendix drive). The solenoid may not be supplying enough power to push the starter gear into the flywheel, or the gear itself may be worn or stuck. Additionally, issues with wiring or a weak battery could also prevent proper engagement. It's essential to diagnose these components to determine the exact cause.