If the battery is fine but the engine won’t start, the starter may be at fault. Warning signs and simple checks of the solenoid and armature.
If the battery is healthy but the engine will not start, the starter is a prime suspect. MSG Equipment explains checks that can be done without a test bench. Typical signs: a single loud click, the pinion not engaging the flywheel, the starter spinning freely, or the pinion not retracting after the engine starts.
- Solenoid: with the starter removed, connect the solenoid terminal to battery positive and the housing to negative; a good solenoid clicks and pushes the pinion forward. If not, suspect burnt contacts, windings or a jammed plunger.
- Armature: measure insulation resistance between the housing and windings; megaohm readings mean it is sound, near-zero values indicate a short.
If these checks pass, the ignition system should be inspected too.