You hear a click from the starter solenoid but the engine doesn't crank. Starter motor worn out (common after 3,000-5,000 hours) or bad electrical connections to the starter.

What you'll see

You press the start button and hear a solid click from the starter solenoid -- but the engine doesn't turn. Or the starter engages but turns very slowly even with a fully charged battery. Sometimes the starter motor spins but doesn't engage the flywheel (you hear a high-pitched whirring without the engine turning). These are all starter motor problems.
Before you assume this is the problem

Before blaming the starter motor, confirm the battery is good (voltage under cranking load above 10V). A weak battery causes the same symptoms. Also check that the engine isn't mechanically seized -- try turning it by hand on the crankshaft pulley bolt. See: Weak or Dead Battery.

See all causes of engine won't start →

How to diagnose

  1. Listen to the starter behavior

    Click but no crank = solenoid engages but motor doesn't turn (worn brushes, bad armature, or mechanical jam). Whirring without cranking = Bendix drive not engaging flywheel (worn gear teeth). Nothing at all = solenoid not getting power (check wiring). Slow cranking with good battery = starter is dragging (worn bearings or brushes).
    Result: Identify which failure mode to narrow the diagnosis.

  2. Check voltage at the starter motor

    Measure voltage at the starter motor's main terminal while someone presses the start button. You should see battery voltage (12V or 24V). If you see significantly less, there's a bad connection in the cable path from battery to starter. Check the battery cables, any junction points, and the ground connection to the engine block.
    Result: Full battery voltage at starter terminal = starter motor itself is bad. Low voltage = wiring/connection problem.

  3. Check the start relay and solenoid circuit

    The start button powers a start relay, which sends power to the starter solenoid. If no click at all, trace the circuit: start button -> start relay -> solenoid. Check for power at each stage. A failed start relay or broken wire in this path will prevent starting.
    Result: Power present at each stage = starter motor fault. Power missing somewhere = circuit fault.

How to fix it

  1. Clean and tighten all connections

    Many 'starter motor failures' are actually bad connections. Remove the main power cable from the starter, clean the terminal and the cable lug with a wire brush, and reattach tightly. Do the same for the battery ground cable where it connects to the engine block. This alone fixes a surprising number of cases.

  2. Replace or rebuild the starter motor

    If the starter motor is genuinely worn (bad brushes, worn Bendix gear, burned armature), it needs replacement or rebuilding. Rebuilding is common for larger starters -- new brushes, bearings, and Bendix assembly. For smaller engines (Kubota, Yanmar), replacement is usually more economical than rebuilding. Match the part number exactly -- starter motors are engine-specific.

Common mistakes

Don't keep hitting the start button repeatedly when the starter isn't engaging properly. Each failed attempt heats up the starter motor and can burn out the windings permanently. If the starter has been abused by oil-flooded starts (the screw element was full of oil, making the engine very hard to crank), the starter may need replacement sooner. Check and repair the oil stop valve to prevent future oil flooding.

Parts & tools

Multimeter. Socket set for removing starter. Wire brush for cleaning terminals. Replacement starter motor (match engine model). Anti-corrosion compound for electrical connections.

Review safety precautions before starting →

Safety

The starter motor carries the full battery current -- 200-400 amps. Disconnect the battery before working on starter connections. A loose cable can arc and cause burns or fire.