Starter Motor!

Starter motor

A starter is an electric motor that turns over or "cranks" the engine to start it.
A starter consists of the very powerful DC electric motor and the starter solenoid that is usually attached to the motor (see the picture). Inside, a typical starter motor has the electric windings (coils) attached to the starter motor housing and the armature (the rotating part) that is connected through the carbon brushes in series with the windings. 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.

Starter solenoid

The starter solenoid works as a powerful electric relay - when activated, it closes the electric circuit and sends the battery power to the starter motor. At the same, the starter solenoid pushes the starter gear forward to mesh with the engine's flywheel. A typical starter solenoid has one small connector for the control wire (the white connector in the photo) and two large terminals: one for the positive battery cable and the other for the starter motor.

Battery cables

A starter motor requires a very high current to crank the engine, that's why it's connected to the battery with thick (large gauge) cables (see the diagram). The negative (ground) cable connects the "-" battery terminal to the engine cylinder block close to the starter. The positive cable connects the "+" battery terminal to the starter solenoid.

How a starting system works:

When you turn the ignition key to the Start position, the battery voltage goes through the starter control circuit and activates the starter solenoid, which in turn energizes the starter motor. At the same time, the starter solenoid pushes the starter gear forward to mesh it with the engine flywheel. The flywheel is attached to the engine crankshaft. The starter motor spins, turning the engine crankshaft allowing the engine to start.

Neutral safety switch

For safety reasons, the starter motor can only be operated when the automatic transmission is in Park or Neutral position; or if the car has a manual transmission, when the clutch pedal is depressed.
To accomplish this, there is a Neutral Safety Switch installed at the automatic transmission shifter mechanism or at the clutch pedal in case of a manual transmission. Often a transmission range sensor - the part that tells the powertrain computer which position (P R N D) the transmission is in, is used as a neutral safety switch (in the photo).
When the automatic transmission is not in Park or Neutral (or when the clutch pedal is not depressed), the neutral safety switch is open and the starter control circuit is disconnected.