| A Starter Motor is an essential part of the car that is also part of why the engine is fired up. It is powered by an electromagnetic field which is charged by the battery that cranks the flywheel to make the car run.
It’s bolted to the engine connected to the flywheel via the pinion ring gear. You may not find it on the engine when you open the bonnet, but some of them can be diagnosed immediately and here are some ideas to check its functions finding out also some of its faults. |
The basic science behind the Starter Motor has little similarities to the alternator, while the later charges the battery when the car is the running. The starter motor is the one that makes the engine run when you crank the key or press the start-stop button.
Diagnosing a Starter Motor
Let’s face it that the Starter Motor can’t be easily accessed in the modern car. With the ever-changing and evolving technology, it becomes challenging to diagnose it, but the process of checking its functions are still the same when trying to finding out if its working or not.
But with older cars with analog starter motors, you’ll get to learn the basics on how to diagnose them in finding out their faults. The most important part when you start checking them is having your workshop manuals and ensure to follow the safety protocols before going through observing and inspecting this essential part of the car.
The Right Tools for the Job
In checking the Starter Motor what you need is the right tools to find out if it’s functioning and also probing its connections if other components that are connected to this unit if it’s working properly. The tools you need for this is a test light, multi-meter, and current clamp.
A digital multimeter is quite handy it's most suggested if you’re getting one, the Fluke is the best paired with the Current Clamp. A Current Clamp is a useful tool as some wires don’t need to be disconnected and you just clamp the device to find out the readings for the connections.
Your Solenoid Observations
Let’s say the scenario is that the Starter motor doesn’t crank immediately and you think there’s something wrong why it doesn’t function the way you’re used to when you start your engine in the morning. The first thing you do is check the connection from the “thin wire,” which is actually connected to the ignition with the test-light.
When you plug the test-light to check for connections the wire lead is clamped to the ground side of the battery while the pointer is probing the connection of the “thin wire” connecting to the starter motor. If it lights up it means the “thin wire” is functioning properly by cranking the ignition key.
The next thing you check is the Starter Motor’s continuity from its connectors. The first you check is the Solenoid that is bolted on top of the Starter Motor. It’s where the “Thin Wire” is connected.
The function of the “Pull-in” windings is where you pre-engaged the Starter Motor. This is where you crank the key that energizes the Solenoid, which pulls the plunger in. This shifts the pinion into mesh with the ring gear and then closes the switch contacts to operate the starter.
So to check for the continuity of the “Pull-in” is you use the Multi-Meter, where you use the positive side to where the “thin wire” is connected and the ground probe to the body of the Solenoid. The setting for the multi-meter (preferred the Fluke brand) is the continuity setting where you hear a beep if it’s working. If you hear a beep it means the “Pull-in” is functioning.
Next check is the “Hold-In” winding where you probe for the B+ connector where the “Fat Wire” is connected and you don’t need to disconnect this wire. You still have the positive side of the probe connected while the ground probe to where the “Fat Wire” is connected and same settings on the multi-meter if you hear a beep it means the connection from the B+ wire is working.
The third inspection is you need to remove the Starter Motor, which you need to dismantle the Solenoid, This is where things get more intense but usually, you put the multimeter probes on the big connections and you need to push the plunger in to check for continuity. But that would be a bit extreme so this exercise is checking only for the “Pull-In” and “Hold-In” winding for the Solenoid. The third inspection is not needed necessarily unless you dismantle the Starter Motor.
Getting to the Starter
You connect the “Thin Wire” to the Solenoid and attach the Current Clamp to the wire that connects to the battery set to measure for the current drop, while the multi-meter set to the voltage the probes connected to the positive and ground side of the battery. Since there’s no actual spec for the voltage and amperage readings usually the readings for the voltage should be between 150 to 250 volts.
When you check for these results you may need an extra hand to crank the key to start the ending to get your findings. On the initial test crank the engine of the EA Falcon to get the readings and we get 170 volts from the multi-meter at 125 A from the Current Clamp shows that it is in spec.
The last check is you connect the Multi-Meter (set to voltage) from the positive side of the battery to the B+ wire for how much voltage drop. You need to crank the engine again to find out. The spec here is 0.50 volts and the result shows that it is in spec due to the 0.063 volts reading.
Finding Results and Conclusion
Though the Starter Motor readings including checking the Solenoid are in specification, which also shows the connections are working. What this needs is to be overhauled and cleaned for observation.
Usually, if the Starter motor if it’s not working in the modern car they replace the entire unit, but the older cars it’s just fixing and replacing the necessary parts that can still be re-used.
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