How to test a starter motor

How to test a starter motor
How to test a starter motor

Starter motors have a hard job, and I have owned many cars where the starter motor has eventually needed to be changed. 

What normally happens is that you will jump in your car to go somewhere important, turn the ignition key and all that you here is a clicking noise and the car won’t start.

Before you go ahead and strip the starter motor off the car, make sure that you have checked that the alternator and the battery are working correctly.

In the past, I have changed a starter motor and an alternator only to find out that it was a faulty battery causing my starting problems. Also check that all the wiring to the battery, alternator and starter motor (including solenoid) are secure and that there is no corrosion on the terminals.

We will assume that all the other parts of the cars electrics are working fine and that you have already removed the starter motor from the car. See article, how to change a starter motor.

This is a basic ‘bench test’ of the starter motor and solenoid off the vehicle. It is a basic test that should be done before you fit a starter motor, especially if you have purchased one from the scrapyard.

There are other methods of starter motor troubleshooting, these are more indepth and are not covered in this article,

Price up a starter motor for your car

What you need.
A well charged battery
A set of jump leads.

During these test it is quite common for large sparks to be produced. Make sure you are in a clear area where there are no flammable liquids
or other materials.
There is too much torque, safest thing is to mount it in a vice if possible.

Test the solenoid.
The Solenoid controls the movement of the ‘starter motor pinion’. Connect the black jump lead to the negative (-) terminal of the battery and the other end to the body of the starter motor.

Now connect the red jump lead to the positive (+) terminal of the battery and touch the other end of the lead to the terminal on the back of the solenoid.  The solenoid should click loudly and throw the starter motor pinion forward.  The starter motor should not turn.

If this does not happen, then the solenoid is faulty.

Test the starter motor.
Touch the end of the red jump lead onto the large terminal of the starter.
The pinion should rotate strongly (see video below).

This clip shows the starter motor being tested.

When power is applied, the starter motor spins around.

Please leave a comment or advice for others