How to Start a Lawn Mower with a Bad Starter?

It is a great sunny day to work in your garden. You think of setting up the items to start mowing the lawn. Put on the boots, the gloves, and the gardening clothes. You’re ready to mow the lawn right away.

But once you get the mower out of the garage and try turning it on – it just doesn’t. You try several times, but it won’t start at all.

At that moment, you start to suspect it is the lawn mower starter that doesn’t work. What do you do? Easy – you try turning the mower on by bypassing the starter.

Here, we’re going to help you understand how to do this. But we’re also going to show you other problems you may be facing so you can prevent any wasted time and effort. 

Interested in what we can teach you? Then keep scrolling…

What is a Lawn Mower Starter?

lawn mower starter

Automotive starter (solenoid on top and motor on the bottom)

Let’s start by explaining what a lawn more starter is in the first place.

You could say, in short words, that it is the part that brings electricity from the battery into the ignition system. 

But you’ll be surprised to know that most mowers have two starter parts. Here’s a little more about each: 

Starter Solenoid

A solenoid is what receives the current from the battery and transmits it to the motor. 

Once you push the ignition button on the mower, the electrical current is sent from the battery into the solenoid through wiring. This solenoid then creates an electric current it carries into the engine starter itself.

Starter Motor

The starter motor is the one that connects directly to the spark plugs, sending the current from the solenoid to the engine itself. 

An engine starter is usually located close to the solenoid. The whole purpose of this piece is to send the electric current coming from the solenoid in a sufficiently powerful way to create a spark.

The spark is what helps produce the ignition once it passes to the spark plug, sending the spark directly into the gas chamber. The combustion produces the power for the gears inside the engine to start moving – turning the mower on.

As you can see, these two starters are connected. But sometimes, one of them may fail. And when that happens, you may want to find a way to still turn the mower on. 

Next, there’s a small guide about how to diagnose and find the issue.  

Diagnose the Problem First

So, your lawnmower won’t start. No matter how much you push the starting button, it just doesn’t turn the engine on.

What do you do? Well, before thinking whether it is the starter (solenoid or motor), you should check that other parts aren’t the problem. Then, you can check whether it is the starter system that doesn’t work.

Here are a few things you may want to check first: 

1. Battery

The first step into checking a lawnmower that won’t start is the battery.

A battery tends to drain consistently, especially after a certain amount of use (after several months or a year). In that case, the mower won’t start at all.

Sometimes the mower starts, but you get sudden turn-offs and inconsistent power. 

In both situations, there’s a high chance it is the battery probably not working anymore.  

Symptom

The first symptom of a drained battery is the lack of cranking or a very slow crank.

Once you turn the key or push the ON button, the engine should make a clanking sound. If nothing happens when you start the mower, it means the battery is not sending any electricity into the engine. 

A clicking noise may also be a sign of a bad battery, but it could be confused with a bad starter. How do you make sure? You diagnose. 

Diagnosing

Checking whether the battery is drained or defective takes only a few steps. Here’s what to do:

  • Start by charging the lawnmower battery. If you don’t find a battery charger, then you can always jump-start the engine (be sure it is at least a 12-volt battery).
  • Once you start the battery (or jump-started the engine to charge it), then you can check whether it has proper charge.
  • For that, you’ll have to find a voltmeter. This voltmeter should provide a reading of no less than 12.7 volts if fully charged. 
  • If the readings go below the 12.4 volts – then there’s a high chance the battery is malfunctioning.

What do you do here? Easy – you replace it. But if the battery is working correctly, then you may want to keep diagnosing the mower. 

2. Electrical Connections & Wiring

lawn mower starter

 

Another common issue with mowers not starting falls directly into the electrical connections, wires, and similar parts.

Remember that a mower is a mechanical machine that turns on with the gas. This creates enough heat to wear off connections and wires over time. 

Because these wires and connections are directly attached to the starter (motor and solenoid), they are super important to consider. But don’t forget they also connect the starter to the battery, the ignition switch, and so on.

So, even the slightest problem with connections and wiring may cause the mower to not start at all. 

Symptom

What will you experience if any part of the electrical system doesn’t work? Well, it depends.  

But the most definite sign of defective wires/connection is when the engine doesn’t turn on at all. Instead, you get sparks and/or light clicking. 

Diagnosing

Diagnosing this is not easy, because there are way too many connections and cables to look to. But you can do so by following these steps:

  • Open up the lid of the lawnmower. Use a screwdriver as needed. 
  • Look for a wire brush and clean all the electrical connectors inside. 
  • Trace the wires as you clean. Make sure everything connected correctly.
  • Check everything from the switch/start button to the battery, starter, and even up to the spark plug connector. 
  • If you see any connection loose, or a wire damaged/broken, then that’s the issue. Fix accordingly.

If you don’t see anything while cleaning and tracing the wires, then the problem is something else. 

3. Spark Plugs

how to start a lawn mower

Spark plugs can also be the problem behind a mower not starting correctly. Because they’re what creates the spark inside the combustion engine, they need to be functioning at all times.

Symptom

What often happens when a spark plug doesn’t work is that you listen to the clicking sound from the starter, but don’t hear any humming from the engine.

You may also hear the spark inside the engine, but something so minimal that it doesn’t start the engine at all.

Diagnose

To make sure it is the spark plug causing the problem, you will need to do this:

  • Remove the wire on the spark plug. Check that the wire contacts are not worn out or burned.
  • Then get the spark plug out of the engine. You will probably need a socket wrench to do so. 
  • Check the spark plug ends. The inside end of the engine should be clean or at least not carbonized or oily.
  •  If you spot any sign of damage or wear, then you’ll have to replace it. Remember to pick the right spark plug for the lawn mower. 
  • In case you didn’t find a physical problem with the spark plug. Then check the spark plug on another mower, or try using a new one on the same mower. If it works, then you’ll have to use the new one instead. 

If you don’t see a problem while checking the spark plug, and it doesn’t work when you use a new one, then it means it is the starter not working. 

4. Starter (Solenoid or Motor)

The starter is mounted between the battery and the engine. It is made of the solenoid that energizes the motor. Together, they help create the spark by sending it to the spark plug.

When the starter doesn’t work – then the mower won’t start at all. In that case, you’ll have to replace it or bypass it. 

Symptom

The signs of a bad starter are several:

  • If the solenoid works but the motor doesn’t, then you’ll hear a constant clicking sound from the solenoid – but nothing else.
  • If the solenoid doesn’t work, then the clicking sound will only sound once.
  • In case the starter is broken or improperly grounded, then you’re likely to not hear anything. 
  • In some cases, you hear the clicking and whirring from the starter, but the engine never engages. 
  • If the engine starts for a few milliseconds (or seems to almost turn on), then it probably means the starter motor gear is broken. 
  • And lastly, if the engine stutters after listening to the whirring sound, then it probably means the starter is dirty and needs cleaning. 

We know this is a bit confusing. Luckily, you can diagnose exactly what the problem is by 

Diagnose

Diagnosing the starter on a lawn mower is not a piece of cake. But it is possible. You just need to follow these steps carefully:

  • Start by testing the solenoid. We recommend attaching a jumper wire from the lug that connects to the battery (solenoid) to the larger lug (motor) directly. Then, try starting the engine. 
  • If the engine starts after attaching the jumper from the battery to the bigger lug, then it means the solenoid is defective. But if the mower doesn’t start, then keep diagnosing.
  • Now attach the jump starter to both the small lug (solenoid) and the large slug (motor). Turn the mower on once again. If the engine doesn’t turn on in the slightest, then it is the entire starter that needs replacement. Otherwise, the problem is the motor. 

In that case, you’ll have to replace the motor from the starter. But we recommend replacing the whole starter instead. 

In case it is the solenoid that is defective, then you can follow the next section. 

How to Bypass the Starter Solenoid

To bypass starter solenoid means trying to start the engine using the starter motor only. Luckily, it is not as hard as it seems.

Here’s how:

  1. The starter is usually tubular (two slugs pieced together). It is composed of the smaller slug, which is the solenoid and the larger lug, which is the motor. You’ll see how the solenoid has one or two wires connected to it that comes from the battery/ignition switch.
  2. You will have to place the metal blade of a screwdriver (insulated) or any similar piece of metal in the connection between the cables that come from the battery/ignition switch to the starter motor. Then, you’ll try turning the mower on.
  3. If you hear a whirring sound from the starter motor, it means you can get the engine on. Keep trying turning on the mower until it does.

The process can be more difficult as it seems, and it may not turn the lawn mower on at all. But as long as it is only the starter solenoid that is defective, it should turn on sooner or later. 

Bottom Line

When the lawn mower starter is broken, the best solution is to replace it entirely. But you can always try bypassing the solenoid instead and see whether it does the job.

So don’t get demotivated to use your mower if the day seems perfect for that. 

Try following this guide to the letter instead, and you may end up turning the mower on without needing the starter at all.

Brice The Botanist
 

Growing up in Ventura, California famous for it's rich gardens. Brice has spent most of his life trying to help make the world greener. Studying Botany at CSRA, he's made it a lifelong passion to greenify every home.

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