Starter Motor Testing

Before you test the Starter motor, you have to check to make sure that the battery is clean e.g. the terminals are not rusted or corroded.

After that, you check if the battery is charged. To do this, you connect a voltmeter to the terminals. 12.6/7 Volts means that the battery is fully charged. Then, you disconnect the distributor so that the car won't start. Turn the key and the voltage should drop to around 10 - 11.

Next, you check how many amps are flowing from the battery to the starter motor. You do this by putting an amp reader over the cable that leads from the battery to the starter motor, it should read under 175 amps.

To check the voltage drop from the battery to the starter, you connect the positive wire to the starter motor and keep the negative wire on the negative terminal. Voltage drop should be roughly  0.2 Volts.

To measure the voltage available at the starter motor you subtract the voltage drop from the amount of volts that the car is putting out. For example, if the car was putting out 11.2 Volts and there was a drop of 0.2 Volts, your voltage available would be 11 Volts.

For the amount of volts to the ignition terminal on the starter motor, you connect the positive wire to the ignition terminal and the negative wire to the negative terminal on the battery.

Lastly to check the voltage drop through the negative terminal of the battery, you keep the negative wire on the negative terminal of the battery and connect the positive the wire to the engine block. The voltage drop should be around 0.2 - 0.3 volts.