How To Bench Test A Riding Lawnmower Starter (Step-by-Step Guide)


How to Bench Test a Lawnmower Starter

Here’s the scene: you just pulled your riding lawnmower out for the first mow of the spring season, and you turn the key, but nothing happens. You hear some clicking, but the engine doesn’t turn over. You try again, and the same thing occurs.

Usually, when this happens, the battery is to blame. However, if you know that your battery is good, the issue could be with the starter motor. This motor receives power from the battery and helps turn the flywheel and crankcase. If the motor is faulty, it won’t turn the flywheel correctly, which prevents the machine from starting.

Before replacing your starter motor, it helps to test it to be sure that it is the source of the problem. You will have to remove the motor and hook it up to your mower’s battery directly.

Alternatively, you can use a battery jumpstart pack to do this. Simply connect the positive and negative wires to the starter. If it spins with no issues, the component is still in good shape. If it doesn’t spin or does so erratically, you have to replace it.

Overall, this project is relatively complicated but doesn’t require too much know-how or specialized tools. We’ll walk you through the steps to bench test your lawnmower starter and, if necessary, replace it.

What You’ll Need to Bench Test a Lawnmower Starter

  • Work Gloves
  • Jumper Cables
  • 12-Volt Battery
  • Screwdriver Set
  • Nut Driver Set

Step by Step Guide to Bench Testing a Lawnmower Starter

Step One: Position the Mower

You will want to work on a flat, level surface. We also recommend working indoors (i.e., a garage) so that you aren’t exposed to the elements while doing this job. Turn the mower off and remove the ignition key.

Step Two: Access the Battery

Typically, lawnmower batteries are located underneath the driver’s seat, but it might be underneath the front hood. Refer to your owner’s manual if you have trouble finding it.

Step Three: Disconnect the Negative Terminal

You don’t want electricity flowing to the starter motor when removing it, so you will need to disconnect the negative terminal. You do not have to remove the positive terminal, as the circuit will be open, so there is no danger.

Be sure to tuck the wire away from the battery so that it doesn’t accidentally touch the terminal. If that happens, it could damage the system or the battery itself.

Step Four: Access the Starter Motor

Depending on the type of riding lawnmower you have, you will likely have to remove various elements to get to the starter motor. This piece is usually next to the flywheel assembly since it powers the crankshaft directly. In most cases, you’ll have to remove the following pieces:

  • Air Duct
  • Air Filter Cover and Filter
  • Blower Housing
  • Lower Dash

You should see the starter mower after removing all of these pieces. Again, refer to your owner’s manual for an exact location.

Step Five: Disconnect the Starter

There is a mounting bracket that holds the motor in place, as well as a wire that feeds into the flywheel assembly. Disconnect both of these to remove the motor.

Step Six: Mount the Starter in a Bench Vise

You will need to hold the motor in place when testing it, as it will vibrate and shake around. A bench vise is ideal, or you can simply hold it with your hands while testing it. If you opt for the latter tactic, we recommend enlisting a friend’s help to make it easier.

Step Seven: Connect the Starter to a Battery or Charger

If you connect to a battery directly, be aware that the motor will start spinning immediately. If you have a battery charger with jumper cables attached, we recommend using that because you can switch it on and off at will.

There is a positive terminal on the bottom of the starter motor. This is where the wire should have been attached. The mounting bracket acts as a grounding rod, so there is no official negative terminal.

Connect the negative side of the jumper cables (black) to the mounting bracket. Then, connect the positive side to the terminal. If you’re using a battery, the motor will start spinning (if it works). Otherwise, turn the charging unit on to see if the starter activates.

As we mentioned, if the motor spins with no problems, then your starter isn’t the culprit. However, if it stops suddenly or spins erratically, you will have to replace this component. Fortunately, if you have to get a new motor, you can simply attach it and reverse the steps above to install the new starter.

Safety Tips When Bench Testing a Starter Motor

Whenever you are working with any electrical components, we highly recommend following these safety tips.

  • Wear Gloves – Thick work gloves can insulate your hands in case of an errant spark or shock.
  • Be Aware of Completing a Circuit – Once the positive and negative terminals are connected to a conductor (i.e., metal), electricity will flow through. So, be careful not to touch the jumper cables to anything before testing your starter. If you do, you could damage the battery or cause injury to yourself.
  • Inspect the Motor and Battery for Corrosion – Even if the starter motor works, it could still be rusted or corroded. There is also a plastic gear piece that connects to the flywheel to make it turn. If the gear is worn down, you will have to replace that for the component to work correctly. Never put dirty or grimy components back into the engine – always clean them first.

Other Electrical Components to Test and Inspect

There is an entire electrical system within your riding lawnmower, and the starter motor is just one piece of it. Here are the other elements that could be causing you trouble when trying to start your machine.

  • Battery – Nine times out of ten, the battery is to blame for a non-starting mower. Either it is too old, or the cells have been drained. This usually happens when the mower has been sitting for a long time. The battery provides power to the starter, so if it is dead or doesn’t have enough voltage, the lawnmower won’t engage.
  • Solenoid – Some riding mowers have a starter solenoid. This piece regulates the amount of electricity flowing from the battery so that it doesn’t overload the starter. If the solenoid is busted or faulty, it could prevent your mower from turning on.
  • Voltage Regulator – As the flywheel spins, it generates an alternating current, which flows into the voltage regulator. This piece then converts the A/C power to D/C to recharge the battery. While a faulty regulator won’t necessarily prevent your mower from starting, it may cause the battery to drain faster.
  • Wires – Multiple wires connect each electrical component to the next. One wire goes from the battery to the starter motor. Another set goes from the flywheel assembly to the voltage regulator, where a third wire connects back to the battery. If any of these pieces are worn or rusted, the circuit won’t complete. If that happens, your lawnmower won’t go anywhere.

Alternative Reasons Why Your Mower Won’t Start

If you have bench-tested the starter motor and it is working properly, you might want to inspect these other components to see if they are causing problems with the engine:

  • Spark Plug – Realistically, you need to change your spark plug once per season. If you haven’t done this in a while, the piece could be damaged or corroded. When that happens, the fuel won’t ignite, which means that the mower doesn’t start.
  • Carburetor – Unlike modern cars, lawnmowers use a carburetor to mix air and gasoline. If the carb is dirty or busted, it won’t allow the right mixture to flow through the system.
  • Fuel Filter – This component ensures that the gasoline mixing into the carburetor is clean. If the filter is clogged, no gas can go through.

Related Questions

Should I replace my battery if the starter is bad?

Not unless the battery is old or corroded. If you have a multimeter, you can test the voltage output from the battery. As long as 12 volts are coming out of it, you should be okay. If the output is less than that, however, the battery is no good.

How do I know that the starter is faulty?

We recommend testing each electrical component before moving to the starter. However, bench-testing it will let you know whether the piece is faulty or not. As we mentioned, the battery is often the culprit, so start there.

Upgraded Home Team

We are a team of homeowners and home improvement enthusiasts who enjoy sharing decorating, gardening, home improvement, and housekeeping tips with other homeowners! Whether you're looking for advice on furnishing your living room or the next outdoor DIY project, we've got you covered.

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