Introduction: How to Troubleshoot a Faulty Starter Motor

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Video tutorial on how to diagnose the starter on your vehicle. If you are having an issue with the starter or starting circuit, the engine of your vehicle will not turn over. If the engine does turn over, then you are having an issue relating to somewhere else on the vehicle, therefore the starter and starting circuit is functioning correctly. As for starter replacement, you can rebuilt it yourself which is by far the cheapest method and I have a full in depth tutorial on how to do this, have a specialist rebuild the unit, purchase a rebuilt unit, or purchase a new unit. The option of a used replacement also exists, but I am not normally a fan of this as you are unable to determine it’s life expectancy.

Tools/Supplies Needed:

  • multimeter
  • socket set and ratchet
  • battery load tester
  • wrenches
  • screwdriver set

Step 1:

The ignition switch which is the main controller of the circuit. Next is the battery that provides the power to the whole circuit. The solenoid acts as a relay and provides linear mechanical movement, and finally the motor. The ignition switch and solenoid operate on the low amperage circuit while the starter operates on the high amperage circuit. The case of the starter motor assembly is ground or earth. When the ignition switch is turned to the start position, this activates the solenoid that provides mechanical movement and turns on the high amperage circuit providing power to the motor.

Step 2:

Either the power going into the ignition switch, the ignition switch itself, or the wire between the ignition switch and solenoid may have an extra switching device which can be relating to neutral safety switch, clutch switch, or some type of anti theft feature. If it’s an anti theft issue, then most likely you will have some type of light flashing on the dash relating to a security feature.

Step 3:

First check the fuse, use a multimeter or test light to determine if the fuse is faulty. If your vehicle is equipped with a fusible link, this will be known by it’s wiring diagram. A continuity test can be done between two points, but make sure your testing the wiring only with no electronic components in between.

Step 4:

The battery might be either low on voltage or it is unable to handle a load. A load test can be done on a battery to determine it’s condition. Use a multimeter, also test to ensure the engine has a sufficient ground. Not all vehicles will have a relay in the circuit, so refer to your wiring diagram which will determine if the vehicle has one or not. The relay itself can be tested to determine if the coil or contacts are faulty. Next the electrical connector can be tested to determine if it has voltage and a sufficient ground.

Step 5:

On some older vehicles, the solenoid might be separate, but the same testing procedure will apply. Test the voltage at the solenoid switching wire using a multimeter as you turn the key. Battery voltage should be present at the connection. If not, there could be a fault with the wire or a faulty ignition switch if previous areas have passed. Test the main power able feeding the starter assembly which is the high amperage side & should have battery voltage present at all times.

Step 6:

The ignition switch connector can be tested for power, back probed when it’s operated, & also have a continuity test when disconnect from the circuit. If it’s not receiving power, then there is an issue with the wiring or circuit between the switch and battery. Set the multimeter on the lowest ohms setting and test the resistance of the coil of the solenoid. The solenoid also has an internal connection to switch the high amperage circuit. The solenoid may need to be powered up if it doesn’t have a plunger, but do not hold the power on for an excessive amount of time as you can overheat the coil.

Step 7:

If all tests pass above, then you will have a faulty starter motor.

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