How to Test a Lawn Mower Starter

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Last updatedLast updated: March 12, 2021
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All ride-on lawnmowers need on-board batteries to start. The process begins from the ignition key when you turn the key of the lawnmower. Lawnmower engines need a solenoid to start. The starter solenoid acts like the electrical connector. It is an electromagnetic switch that couples an ignition with a starter. The solenoid sends power to the starting mechanism, causing the engine to spin. But when the magnet turns badly, the motor will not turn. A faulty starter will act the same way, so it’s best to test the solenoid before replacing either. Before trying to find out how to test a lawn mower starter yourself, you should know that testing is dangerous, so be extra careful. You’ll have to find the solenoid by following the positive wire from the battery.

How do you know it is time to test a lawn mower starter?

You can suspect you have a bad starter when it starts making cranking noise and not making engine turnover. You can also have a clicking noise when you press the ignition button. Also, if the mower doesn’t respond to starting attempts, you may need to bench test it to know if the problem is from the starter or not.

How to check a lawnmower starter

The starter assembly on a petrol lawnmower started with a pulley includes the starter rope, recoil spring, and the starter pulley itself. They allow you to manually start combustion, starting the engine faster with each pull. If the engine is not responding to starting attempts, below are instructions on how to check the lawnmower starting mechanism.

What you’ll need

  • Screwdriver
  • Wrench

Instructions

  • Step 1: Move the mower to a flat surface. Turn off the power switch. Disconnect the rubber plug from the spark plug and wire against a metal ground tip on the cylinder.
  • Step 2: Depending on the model, you can unscrew the rope guide at the mower handle or near the motor with the screwdriver and wrench. Unscrew the starter fan cover. Take the cover off the top of the engine.
  • Step 3: Remove the starter by holding the cap to see if it unwinds and rolls smoothly. Determine if it is too loose or too tight against the pulley, or bumps into the recoil spring.
  • Step 4: Cut off the starter rope if it looks frayed, oily, or broken and remove it from the pulley. Unscrew the pulley and slide the bolt, washer, and pulley off the post. Flip the cap over and remove the recoil spring, if still attached, with the tip of the screwdriver.
  • Step 5: Inspect the spring inside the cartridge to make sure it is not damaged and the hooks are not bent. Replace the spring if it is damaged. Replace the pulley if it has cracked or broken. Reassemble parts in reverse order after replacing all damaged parts.

How to bench test a lawn mower starter?

What you’ll need

  • An insulated screwdriver
  • A wrench
  • A digital voltage meter
  • A pair of safety glasses

Instructions

How to Test a Lawn Mower Starter

  • Step 1: Bridge the gap between the two large posts on the solenoid valve with an insulated screwdriver. If the starter does not respond, the solenoid, starter, ignition switch, or the battery is bad. If you have a bad battery consider jump-starting it. One of the most recommended by verified users is the TrekPow G22 Battery Jump Starter, thanks to its fast-charging ability and the inclusion of a voltmeter.
  • Step 2: Remove the cable from the small station with a wrench. Set the value of the D/C voltage meter power to 20 volts. Clip the positive cable to the wire and the negative wire to the ground. If the voltmeter does not read at least 12 volts, the solenoid, switch, or ground wire is bad.
  • Step 3: Reassemble the wire with a wrench. Slit the positive wire from the voltage meter to the large positive terminal on the solenoid. Clip the negative terminal of the voltmeter to the ground. If the meter voltage is less than 12 volts, the solenoid is bad.
Tip: Ensure you’re wearing pairs of gloves and safety glasses.  According to most reviews, one of the most popular safety glasses models is the ToolFreak Rip Out Safety Glasses, which features foam padding and resists UV.

How to Change a Solenoid in a Lawn Mower

So, you’ve completed the test and you found out the solenoid is the problem. A broken solenoid will have to be replaced before the engine will start.

Instructions

  • Step 1: Obtain the correct replacement solenoid part for your specific lawnmower. You must have the model number of your mower with you.
  • Step 2: Open the hood or cover on the lawnmower engine to find the battery. It will have a red “positive” wire and a black “negative” wire, coming out of its ends. Use a socket wrench to loosen and disconnect the red wire so you are not shocked and then remove the black wire the same way.
  • Step 3: Find the solenoid between the lawn mower’s starter and the battery. The other end of the red battery wire extends back and connects to one side of the electromagnet. Use your socket wrench to turn the bolt that the wire connects to in a counterclockwise direction. Remove the other wire from the other side of the solenoid valve using your socket wrench in the same manner.
  • Step 4: Take a wide wire harness from the magnetic coil using a utility knife to pry it under and lift the caliper. Lift the small wires that make up the harness to remove it entirely.
  • Step 5: Unscrew the four bolts that hold the solenoid to the machine frame again using your socket wrench. Lift the solenoid.
  • Step 6: Place the replacement solenoid in the lawnmower. Connect the two main wires back to bolts next to the solenoid valve using your wrench.
  • Step 7: Route the wiring harness back over the solenoid and make sure it makes contact with the electrical connectors on the solenoid valve.
  • Step 8: Connect the red and black battery cables to the battery, then close the engine cover

Safety tips

How to Test a Lawn Mower Starter

When jump testing a riding lawnmower’s starter, when an insulated screwdriver is not available, wear heavy, rubber gloves and use a regular screwdriver. Some of the most reliable pairs of gloves are the Gorilla Grip Work Gloves. The slip-resistant glove product is a pack of 5 pairs and they are for all-purpose use.

Final thoughts

Testing the starter is necessary when you have problems starting your lawnmower and you need to know if the starter is bad. It helps you determine when the problem isn’t with the starter and when you have a bad solenoid. So, by simply following the instructions we laid down on how to test a lawnmower starter, you would not make a hurried rush to replacing your starter when it is actually not the problem. You have to diagnose the problem by checking and testing the starter, the solenoid, the ignition switch, the battery, and all connections. All you need are simple working tools like the screwdriver, the wrench, and the multimeter.

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