When does a starter motor need to be replaced?

When you are starting your car, a starter motor turns over your engine. It's a small, heavy-duty electric motor. It doesn't need any maintenance and only needs to be replaced if it's bad.
Car Starter Motor Car starter motor.
How long does a starter motor last? In many cars, a starter motor lasts for the lifetime of the vehicle, but in some cases it may stop working in as little as 30,000 miles.

Why does it fail? A starter motor has several moving and rotating parts. Over time, things like electric carbon brushes, bearings and an overrunning clutch wear out. Electrical contact points inside the starter solenoid become pitted and stop working. What happens if a starter motor fails? You guessed it right; the engine won't turn over. Of course, a failed starter motor is not the only reason why an engine would not turn over. This also could be caused by a weak battery and several other problems. Read: Signs of a weak battery.

Are there any signs that a starter motor is going bad? Yes, but not always; sometimes a starter motor just stops working one day. In some cars when the starter motor is failing, you may notice that the engine won't turn over on the first attempt; it may take several tries before the starter motor engages. Sometimes a worn-out or shorted starter may turn over slower that usual, even if the battery is fully charged or new.
How do mechanics test a starter motor? The old-day trick was to tap a starter motor lightly with a small hammer and see if it works after that. If it did, the mechanic would know the starter motor is bad. Today, mechanics simply measure the voltage at the starter motor terminals. A starter motor has two wires: a small wire for the control circuit and a larger cable connected to the battery. If there is a battery voltage at both terminals when pressing the Start button or turning the key and the starter motor doesn't run, it's bad.

How does the starting system work in a car? First, the car computer checks if the code in the ignition key or fob matches the security system (immobilizer). After that, the computer checks if the transmission is in Park or Neutral or if the clutch pedal is depressed in a car with a manual transmission.
Car Starting system Car starting system
If both checks pass, the computer operates the starter motor through the control circuit and starter relay, see the diagram. The starter motor is powered by the car battery and will work only if the battery has enough charge. If a car doesn't start, the battery must be tested first.

How much does it cost to replace a starter motor? In an average front-wheel drive car like Honda Accord or Toyota Corolla with a small 4-cylinder engine, the labor charge to replace a starter motor varies between $95 and $175. In some vehicles with large engines (e.g. BMW, Cadillac Northstar V8, Toyota V8), an intake manifold or other components must be removed to get to the starter motor and that requires a lot more labor ($260-$450).

An aftermarket starter motor (part) costs $85-$220 plus the core charge. The core charge is a deposit for an old part. Many part stores will give you the core charge refund If you return the old starter motor.
An original or OEM starter motor is more expensive ($270-$480). Recently, one of our friends replaced the starter motor in his 2014 Honda Accord when it started giving him intermittent problems. He paid $390 for an original part plus $127 labor at the dealership.

Can a starter motor be rebuilt? Yes, any local auto electric (Starter & Alternator) shop should be able to rebuild a starter motor. Prices range from $65 to $150 (not including installation). Of course, rebuilding a starter motor takes time.

If a starter motor gear does not mesh properly with the flexplate ring gear, a starter motor may produce a loud grinding noise when attempting to start. In this case, both the starter motor and the flexplate (or flywheel in a manual transmission) ring gear must be inspected. Beside a bad starter motor, this could be caused by worn-out flexplate or flywheel gear teeth. Replacing a flexplate or a flywheel is expensive, as in either case, the transmission must be removed.