Starter Motor

A starter is an electric motor that turns over the engine to start it.

A starter consists of the very powerful DC electric motor and starter solenoid that is attached to the motor (see Figure1).

Figure1 Starter Motor

              
A starter motor requires very high current to crank the engine, that's why it's connected to the battery with large cables (see Figure 2).

Figure 2 Simplified diagram of typical starting system

The negative (ground) cable connects the "-" battery terminal to the engine block close to the starter.

The positive cable connects the "+" battery terminal to the starter solenoid.

The starter solenoid works as an electric switch - when actuated, it closes the circuit and connects the starter motor to the battery. At the same time, it pushes the starter gear forward to mesh with the engine's flywheel.

How the 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. The starter motor cranks the engine.

A starter can only be operated when the automatic transmission shifter 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 transmission shifter or at the clutch pedal.

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 relay disconnects the starter control circuit.

Car starting problems

If when you turn the key to the "Start" position, you hear the starter cranking as usual, but the car doesn't start, then the problem is most likely not with the starting system - check Car no-start troubleshooting guide.

If when you turn the ignition key to the "Start" position and nothing happens, or all you hear is just a click, or the starter cranks very slow then you probably have a problem with one of the component of the starting system. Most often, it's the battery or the starter motor itself.