Starter Motor Guide

Diagnosing a failing starter motor

Slow cranking can also be caused by a discharged battery, corroded battery terminals, or a faulty earth strap. Eliminate these cheaper causes before replacing the starter.

• Single loud click when the key is turned — solenoid engaging but motor not rotating
• Repeated clicking — solenoid cycling rapidly due to voltage drop under load
• Slow, laboured cranking despite a healthy battery — worn motor brushes or armature
• Grinding during cranking — worn Bendix drive or damaged ring gear
• Starter spins but engine does not crank — Bendix drive not engaging the ring gear

Replacement procedure

The starter location varies considerably by engine layout. On many transversely mounted engines it is at the front of the engine above the gearbox bell housing; on longitudinally mounted engines it is at the rear below the exhaust manifold. Disconnect the battery first. Note the wiring orientation before removing — the main cable and solenoid trigger wire must be reconnected correctly.

Check the ring gear teeth for damage before fitting the new starter — a ring gear with missing or severely worn teeth will damage a new Bendix drive within weeks.

• Measure battery voltage and cranking current before condemning the starter
• Check the battery earth strap and engine-to-body earth cables for corrosion
• Inspect the solenoid contacts — they are serviceable on many starters and are inexpensive to replace
• Smear a thin coat of copper grease on the mounting bolts to prevent seizure

Frequently Asked Questions