How to Bench Test a Lawnmower Starter, step by step

If you have problems starting your lawnmower, one of the potential issues could be the electrical system. If you do not hear anything when you press the starter button, a faulty starter could be the reason. Other potential reasons could some loose or corroded wires or a problem with the starter motor. If you checked the various causes and no real problem has turned up, the next step is to bench-test the starter. Testing a starter is not difficult, but the only bad news is that a faulty starter cannot be fixed and replaced with a new one. This blog post will explain how to test a Lawnmower starter.

How to Bench Test a Lawnmower Starter, step by step:

• Step 1. Collect the needed tools: jumper cable, wire brush, battery
• Step 2: Park the mower on an even surface and turn it off.
• Step 3: Disconnect the spark plug cables
• Step 4: Remove the starter and clean it thoroughly. Make sure you remove all the rust and dirt.
• Step 5: Connect a 12-volt battery to the starter using jumper cables
• Step 6: Test the starter. If the starter is fine, its head should start spinning when connected to the battery. If the starter is clicking or stops automatically, it is faulty and needs to be replaced.

Check the various reason a lawnmower is not starting

A lawnmower with a bad starter won’t start and need to be replaced. But before you start with this job, you should first check if it really is a faulty starter. There are also other lawnmower electrical components that can prevent the machine from starting correctly.

• Battery: Make sure the battery is charged and the connections are all fine. If you are not sure, use a battery tester to see if the battery is still ok.
• Electrical connections: Make sure that the wires are not broken or corroded. You can use a multimeter to check the wires. Use the resistance setting or special setting to check connections.
• Solenoid: Ensure that the starter solenoid is alright and the current is reaching the starter motor.

Except for electrical problems, your mower can also fail to start because of other engine-related issues. If you hear the starter motor working and trying to start the engine, the electrical part is working. Not starting can mean a problem with the sparkplugs, the carburetor, the air filters, or you can have bad gas. These issues are outside the blog post’s scope but are discussed in more detail in other blog articles on this website.

● Lawnmower Battery

The battery of a lawnmower is an important part of the electrical system. It is responsible for providing power to the ignition system and starter motor. A faulty battery means no current will reach the starter, and the mower won’t start. To ensure it is ok, we will check the battery first. The battery needs to be charged and optimal to deliver the energy needed to start the engine. Most mowers use a 12 Volt battery. Use a battery tester to check the condition. If the tester shows that the battery needs charging, you should recharge it. If it shows that the battery is not ok, replace it.

You can also use a multimeter to check the battery voltage. If you see a voltage between 12.7 to 12.9 Volts, it means all is ok. If you see a voltage lower than 12 Volts, it indicates that the battery does not have enough energy. Try to charge it first. If that does not help, replace the battery.

● Lawnmower Electrical Connections

The electrical connections are responsible for supplying current from the battery to the starter. Suppose the electrical connectors or wires are loose, corroded, or broken. The lawnmower will not start. In that case, the flow of electricity is interrupted or reduced. You can use a multimeter to check the various connections and wires. Use the resistance setting and measure the connection. For most connections, the resistance should be less than 1 Ohm. Much higher resistance means that there is something not ok. Use a wire brush to clean the different electrical connectors. Make sure that all the wires are clean and not broken. You should replace broken and corroded wires with fresh wires.

● Lawnmower Solenoid

Solenoids play an important role in starting a lawnmower. When the ignition key is turned, the battery’s voltage enables the starter solenoid. This is a remotely mounted switch that activates the starter motor. It enables the high current needed to power to the starter motor. If the solenoid is defective, the starter motor will not turn. When you try to start the mower with a bad solenoid, it will make clicking sounds. 

You can check the starter solenoid by connecting a jumper wire from one large lug to the other. Connect the battery cable to one of the large lugs and the engine starter cable to the other one. If the starter motor turns over, then the starter solenoid is faulty, and you need to replace it.

After you have checked the various components, and this did not solve the problem, we need to check the starter.

Step by step guide to Bench Testing a Lawnmower Starter

A starter is a motor that is connected to the engine crankcase. The starter starts the mower by turning the engine flywheel teeth with the starter motor plunger’s teeth. Once all the other components are checked and found to be in perfect working condition, the problem is definitely with the starter. It is likely that the magnets, brushes, and springs that contact the wire inside the motor are dirty or worn out. A bad starter has some signs to help identify it. If the connection between the solenoid and the battery becomes loose, you will only hear a clicking sound. When the engine’s rumble does not follow up a whirring sound made by the lawnmower to start it, it means there is a problem with the starter.

Follow the step by step procedure to bench test your lawnmower’s starter:

● Step 1: Collect the needed tools

You will need the following tools to perform the bench-testing task.

• A cleaning brush
• A battery
• A jumper cable

● Step 2: Park the mower and turn it off

Park your lawnmower on an even surface and remove the key.

● Step 3: Disconnect the spark plug cable

Disconnect the spark plug cable. This will ensure that the lawnmower does not unintentionally start.

● Step 4: Remove the starter and clean it

Locate the battery and starter. The battery is easy to find and can be under the hood or under the mower’s seat. The starter can be more challenging to find. The best method is to follow the cable from the battery to the solenoid. And from the solenoid going to the starter. Generally, it should be under the mower’s hood. Remove the starter from your mower and clean the electrical posts with a wire brush. Ensure you remove all the dust and dirt from the starter, so that clean connections are possible.

● Step 5: Connect the starter to a 12V battery using jumper cables

Take a jumper cable and a 12 volts battery to test the starter motor. The black wire is positive, and the red wire is negative.

A jumper cable has two ends. Connect one end of the jumper cable with the battery—the red wire to the negative terminal and the black wire to the positive terminal.

Make sure you have made the connections correctly to avoid a short circuit or sparks.

● Step 6: Test the starter

Connect the other end of the red wire to the starter’s frame. Connect the other end of the black wire to the terminal of the starter. If the starter is in good condition, its head will start spinning. You will see the starter’s head rise to engage with the flywheel. 

The rotation will stop or sound clicky if the starter is faulty. In that case, you should replace the starter.

Related Questions:

1. Is it possible to start the mower if the motor is fine, but the solenoid is faulty?

Yes. It is pretty simple as both the solenoid and the starter are connected in series. You can bypass the solenoid, and the mower will start perfectly fine. It is still recommended to fix the solenoid. But as a temporary solution, you can start your mower and use it for your mowing session.

Final Remarks:

We can see that bench testing a mower starter is not difficult and can easily be done at home. Before removing the starter and testing is you should first check some other lawnmower parts. Clean all connectors and wire endings properly and establish appropriate connections with no loose ends. If the starter is faulty, it needs to be replaced. Following the step-by-step process mentioned above should help you identify the problem, fix it, and end up with a good working mower.