What can excessive use of the starter motor in a difficult-to-start engine cause?

Excessive use of the starter motor in an engine that is proving difficult to start can lead to overheating of the starter motor. The starter motor is designed to operate for a limited time during the engine start process. If the engine does not start after extended cranking, the starter motor remains engaged for too long, which increases its temperature due to continuous electrical current flowing through the motor and resistance from friction in its components. Overheating can damage the starter motor's insulation, lead to electrical failures, or physically deform components, potentially resulting in its malfunction or failure.

This overheating mechanism is particularly critical because it can result in permanent damage that may require replacement or extensive repairs to the starter motor, impacting the overall reliability of the aircraft's starting system. It's important to follow the manufacturer's guidelines regarding maximum cranking times and cooldown periods to mitigate this risk.