First: confirm it is the starter
A car that will not crank is far more often a battery or connection problem than a starter problem. Before buying anything:
- Test the battery under load, not just its resting voltage
- Check the main positive cable and the engine-to-body earth strap for corrosion and tightness
- Measure voltage at the starter's main terminal while cranking — a large drop points at cables, not the motor
- Check the ignition switch, starter relay and any immobiliser or neutral-safety interlock
A single loud click with no crank is often the solenoid pulling in but the motor not turning — which can be the starter, or can be insufficient current reaching it.
Reading the symptom
- Rapid clicking. Almost always insufficient current: battery or connections.
- One solid click, no crank. Solenoid engaging, motor not turning. Worn brushes, a dead armature segment, or a current supply problem.
- Whirring with no engine turn. The motor spins but the pinion is not engaging — worn drive, damaged pinion teeth or a failed one-way clutch.
- Grinding on start. Pinion or flywheel ring gear tooth damage. Inspect the ring gear before fitting a replacement starter, or you will damage the new one too.
- Slow, laboured cranking. Usually battery or cables; can be a tired motor or a mechanical drag in the engine.
Visual inspection of a used unit
- Housing and nose cone. Cracks around the mounting flange are a hard no — this is a heavily loaded joint.
- Mounting face. Must be flat and undamaged. A starter that does not sit square will chew the ring gear.
- Pinion teeth. Chipped, rounded or heavily worn teeth mean the drive has been engaging badly.
- Terminals. Heat discolouration, corrosion or damaged threads on the main stud.
- Solenoid body. Dents, cracks, or evidence of water ingress.
- General condition. Heavy oil contamination suggests it has been sitting under a leak, which does the internals no favours.
Bench testing
A bench test on a used starter typically covers:
- Solenoid operation. Does it pull in cleanly and hold, and does the pinion throw fully?
- Pinion return. Does the drive retract properly when power is removed?
- Motor operation. Does it spin freely, at sensible speed, without excessive sparking or noise?
- One-way clutch. Does the drive lock in one direction and free-wheel in the other?
- No-load current draw. A figure well above normal points to a mechanical drag or an electrical fault developing.
A no-load bench test does not reproduce the load of cranking a cold, high-compression engine. A starter can pass a bench test and still struggle on a cold morning if the brushes are near the end of their life. Brush wear is the failure mode that bench testing is least good at catching, which is why we assess overall condition and donor history alongside the test rather than treating the test as the whole answer.
Confirm the specification
- Engine and fuel type. Diesel starters are heavier duty and are not interchangeable with petrol units on the same model.
- Tooth count on the pinion and the direction of rotation.
- Mounting pattern — bolt count, spacing and nose length.
- Terminal layout and connector type.
- Stop-start systems. Vehicles with idle stop-start use starters built for far more cycles. A conventional starter is not a substitute.
Before you fit it
- Inspect the flywheel ring gear for damaged teeth — turn the engine over by hand and check all the way round
- Clean the mounting face and the earth path; a starter earths through its housing
- Fit the correct cable terminals and torque them properly; a loose main terminal generates heat and fails
- Replace the battery if it is marginal — a weak battery is hard on any starter
What we do before a starter leaves us
Visual inspection of housing, nose cone, mounting flange and terminals; pinion and drive gear condition including tooth wear and free rotation; solenoid operation and pinion throw; bench test for motor operation and no-load current draw; plus photographs of the actual unit.