Starting system, Starter motor
not with the starting system - read our car no-start troubleshooting guide for tips how to find a problem. Here are a few common starting system problems:
Corroded batter terminal Good connection
The battery is very common to fail. Sometimes one of the electrical components that was left on or has a defect causing parasitic current draw drains the battery. Sometimes, an old battery can just die one day, with no warning. In either case, if the battery is low on charge, it won't have enough power for the starter motor to turn over the engine.
If the battery is low on charge, when attempting to start the engine you will probably hear a single click or repeated clicking, or the starter may turn over slowly and stop.
Poor connection at the cable terminals can cause the starter not to work or run very slow too. Often the battery terminals or the ground cable connection get corroded causing starter problems (see the photo).
Corroded starter solenoid control terminal
Sometimes the starter control terminal gets corroded (in the photo) or a starter control wire gets loose or disconnected from the terminal causing the starter not to work. For example, this corroded starter control terminal was the cause of a no-start, no-crank condition in the Mazda 3. We only noticed this after disconnecting the control wire connector.
Cleaning the terminal and replacing the connector solved the problem.
Another part that often fails is the starter motor itself. Sometimes the carbon brushes or some other parts inside the starter motor wear out and the starter motor stops working. If the starter motor is faulty, it will have to be replaced, which may cost from $250 to $650. Rebuilding the starter motor is usually cheaper, but takes more time.
Sometimes the starter gear for some reason won't mesh properly with the engine flywheel. This may cause a very loud metal grinding or screeching sound when attempting to start the car. In this case, the flywheel ring gear needs to be checked for damaged teeth.
An ignition switch also fails often. The contact points inside the ignition switch wear out, so when you turn the ignition switch to the "Start" position, no electric current is going through the starter control circuit to activate the starter solenoid. If jiggling the key in the ignition helps start the car, it's possible that the ignition switch is defective.
A neutral safety switch also can fail or get misadjusted. For example, if a car starts in "Neutral" but doesn't start in "Park," the neutral safety switch should be checked first.
How the starting system is tested
A technician checking the battery state of charge
with the battery tester
When the starter motor doesn't work, first the state of charge of the battery, battery terminals and battery cables must be checked. One of the symptoms of a weak battery is when the dash lights go dim when the key is turned to the START position.
The next step typically involves testing the starter control circuit. Your mechanic may start by measuring the battery voltage at the starter solenoid control terminal with the key in the START position. If there is no voltage, the problem is most likely in the starter control circuit (ignition switch, starter relay, neutral safety switch, control wire). If there is a battery voltage at the starter solenoid control terminal with the key in the START position, the starter motor itself could be bad. The starter solenoid control terminal must also be checked for proper connection.
What is inside the starter motor
Starter motor cutaway. Image courtesy of Robert Bosch GmbH
A starter motor has several (typically 4) electric windings (field coils) attached to the starter motor housing from the inside. The armature (the rotating part) is connected through the carbon brushes in series with the field coils.
On the front end of the armature, there is a small gear that attached to the armature through an overrunning clutch. This part is commonly known as the Bendix.
Many starter motor problems are caused by worn carbon brushes or the armature bearings. The contact points inside the starter solenoid also can fail.
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Please note: the information provided in this article is for informational purposes only and cannot substitute for the advice of professional mechanic or authorized dealer. Consult your mechanic, and check your car's owner's manual for safety measures, precautions, warnings, tips and recommendations.