The solenoid is pulling in but the motor is not turning - burnt solenoid contacts, insufficient current, or a seized motor or engine.

The click is the solenoid plunger moving and throwing the pinion into mesh.

If the motor does not then turn, either the heavy contacts inside the solenoid are not passing current, or the current available is insufficient.

Burnt and pitted solenoid contacts are extremely common and are frequently repairable with a contact kit.

A flat battery or a poor connection produces the same single click, which is why the battery and voltage drop tests come first.

A seized engine gives the same symptom too, so confirming the engine turns by hand is worth doing before ordering anything.

Measure the voltage at the starter while cranking. Adequate voltage with slow cranking means the starter; low voltage means the supply.

Connect the meter directly at the starter's main terminal and its body, and crank.

If the voltage there stays reasonably high and the engine still turns slowly, the starter is drawing excessive current or binding internally.

If the voltage collapses, the battery or the cables cannot deliver, and the fault is upstream.

Test the earth path separately - measure between the starter body and the battery negative while cranking, since earth faults are as common as supply faults.

A current clamp on the main cable compared against the expected draw completes the picture and is conclusive.

Because a chipped or worn ring gear destroys a new starter's pinion, and it is only accessible while the starter is out.

The pinion engages the ring gear on the flywheel or flexplate every start.

Worn or chipped teeth cause grinding on engagement and prevent the pinion meshing cleanly.

Damage is often localised, because an engine tends to stop at similar positions.

Inspect through the starter aperture while turning the engine over by hand, so the whole ring is seen rather than the section that happens to be visible.

A damaged ring gear means removing the gearbox or the flexplate, which is a much larger job - and finding it now rather than after fitting a new starter is the point.

Substantially. They are engineered for many times the number of cycles, and some vehicles use a belt-driven starter-generator instead.

A stop-start vehicle may start its engine tens of times in a single journey.

Those starters use uprated brushes, bearings and solenoids, and often a different engagement mechanism designed for rapid restarts.

Fitting a conventional starter to a stop-start vehicle gives a short and expensive life.

Belt-driven starter-generators replace both the starter and the alternator, restarting the engine through the accessory belt, and are a different repair entirely.

The battery type matters equally: stop-start vehicles need enhanced flooded or absorbent glass mat batteries, and a conventional battery fails quickly.

Yes - solenoid contact kits, brushes and drive assemblies are all available, and a contact kit in particular is a very common economical repair.

Burnt solenoid contacts are the single most frequent failure, and contact and plunger kits are inexpensive.

Brush sets wear and are replaceable on most designs, with worn brushes giving intermittent or slow cranking.

The drive assembly, including the one-way clutch, can be replaced where the pinion spins without turning the engine.

Bushes at each end wear and allow the armature to rub, which is repairable but starts to favour an exchange unit.

For fleets, remanufactured exchange starters give predictable turnaround and a warranty, which usually outweighs the saving from a repair.

Extended cranking, a weak battery, poor connections, and oil contamination - all of which make the motor work harder or hotter.

A starter is rated for short bursts with cooling between, and prolonged cranking overheats the windings.

A weak battery makes the motor draw more current for longer, which is the same problem arriving from a different direction.

Poor connections add resistance, so more of the available energy becomes heat rather than rotation.

Oil leaking onto or into the starter from a nearby seal degrades the brushes and insulation.

Where a vehicle needs prolonged cranking, the underlying starting problem is what shortens the starter's life - fixing that saves the next one.

Disconnect the battery before working on the starting circuit - the main feed is permanently live and unfused, and it will vaporise a spanner.

The heavy cable from the battery to the starter carries no fuse and is live at all times.

A tool bridging that terminal to earth causes an arc flash, welds the tool, and can cause a battery explosion.

Disconnect the battery negative first and insulate it so it cannot spring back onto the post.

Support the starter properly during removal; they are heavier than expected and awkward to hold above a hot exhaust.

Note the terminal positions and any heat shields before removal - a misplaced heat shield lets the exhaust cook the new starter.