Why is my lawn mower turning over but not starting?

lawn mower turns over but wont start

It’s right after the monsoon season, and the grass has grown manifold, making your beautiful lawn look unkempt.

So, you bring out the lawn mower to trim the grass, but for some reason, it fails to start even after you pull the starter rope several times. The only solution is to disassemble the unit and check each part to find the source of the problem.

However, this is time-consuming; meanwhile, the grass keeps growing unhindered, attracting all kinds of pests and, worst of all, weeds. That’s why today’s guide details some of the reasons why a lawn mower may turn over without starting, allowing you to resolve the issue swiftly.

Reasons Why A Lawn Mower Is Turning Over But Not Starting

There could be several reasons why your lawn mower engine is turning but failing to start. That said, the problem usually lies with the air intake, spark plug, or fuel tank.

To be sure, you need to conduct a few starter tests to rule out certain issues, making it easier to narrow down the root of the problem. Rest assured, these are common problems with even a healthy mower engine, and troubleshooting the issue will save you the hassle of going to the service center.

Follow the steps mentioned below to get the lawn mower to start again, good as new:

Fuel Line

It would be best to check the fuel system first before moving on to the next step. This will help eliminate some issues, clarifying where the problem lies.

Hence, use starter fluid to make sure the spark plug and the compression system are fine by spraying the liquid into the lawn mower’s engine. The engine should start briefly before dying down if the spark plug and compression are fine.

It would help if you chose an open area (away from the house) that’s well-ventilated before removing the air filter cap. Then, spray the starter fluid, ensuring that it passes through the air intake of the carburetor.

If the engine doesn’t start at all, there must be a problem with the ignition. But if it starts even momentarily, the most likely conclusion is that the issue is with the fuel supply.

Spark Plug

Considering that there is no fueling fault and the problem lies with the ignition, the next step is to look at the spark plugs. For those who don’t know, the spark plug provides the initial thrust, bringing the engine to life.

Occasionally, a wet spark plug can prevent lawn mowers from starting, and cleaning it might solve the problem. Similarly, a clogged spark plug requires a once-over because of oil and carbon deposits.

Moreover, make sure that wire of the spark plug is tightly connected to the plug or remove it altogether and check for signs of damage. In case it has worn out, you’ll have to change the ignition coil and get rid of the failed spark plug.

One way to be sure is to use a tester to check if the spark plug is getting power. If it doesn’t, you’ll need a new spark plug but ensure that it’s compatible with the lawn mower model as no two spark plug wires are the same.

Dirty Carburetor

Often a lawn mower won’t start due to a faulty carburetor as it cuts the gas supply to the engine. However, before you replace the carburetor with a new model, it would help if you check for signs of damage or clogging.

Over time, dirt from grass clippings accumulate on the carburetor, thereby blocking the filters and preventing the gas from reaching the engine. Naturally, cleaning it should clear the blocked fuel system but before putting it back, ensure that the fuel line is in good condition.

Once you’re satisfied, put the parts back and start the engine. It’s important to note that you must also maintain a healthy ratio of gas to air to keep the riding lawn mower in top shape.

Too much gas is just as harmful as bad gas, a wet plug, or a dirty oil chamber.

Air Filter

You must have noticed that the latest riding mowers come with air induction technology for the smooth functioning of the engine. But encountering a clogged air filter is still very much a reality, so you need to be prepared.

The performance of the air filters is integral to the health of the lawn mower because they filter out the dirty air, containing impurities. This ensures that only clean air passes through the engine, reducing the chances of damage to the carburetor or other parts.

Therefore, gardeners who use lawn tractors and modern mowers should know how to clean air filters to prevent the engine from malfunctioning. We recommend that you remove the air filter cover to monitor the condition of the filters after every 25 hours of heavy use.

If you don’t use the lawn mower much, cleaning it involves a simple procedure. You can bang the filters gently on a wall or with a stick, while some prefer soapy water to remove the dust and grime. That said, it would be best to opt for a replacement if you have paper filters.

Additionally, compressing the air filters might help, but you’ll need to replace them in a dusty environment after 100 hours of use.

Fresh Gas

Have you added fresh fuel to the riding mower, but it still won’t start? This could happen if the lawn mower was lying unused for several months, in which case, pouring fresh fuel into the tank may not work.

The best practice is to drain the old gas from the gas tank and empty the gas valves. Proceed to clean the inside of the tank thoroughly before adding fresh gas into the gas valve.

What’s more, some people add a fuel stabilizer when they aren’t planning to use their tractor mowers for a long time to prevent any fueling system fault. Other than that, you could try replacing the fuel filter, especially if it’s one year old.

Most mower parts gather debris after regular use, and a clogged fuel filter will cut the gas supply to the carburetor. Speaking of the carburetor, be sure to check the fuel line that runs from the tank to the carburetor for signs of damage.

Also, the latest models come with a fuel pump, and you should replace it when it fails to pass gas through the fuel line.

Another part you should check is the fuel solenoid valve that has a wire harness connection. But why is this important? Thanks to this valve, the engine doesn’t backfire when you shut down the power because it stops the fuel supply to the carburetor.

Understandably, a disconnected wire will fail to open the valve, preventing fuel from reaching the carburetor, so check the connection before working.

Flywheel Key

When there is no issue with the ignition coil, the normal conclusion is that the spark timing is off. You should know that the ignition coil and the flywheel magnet are responsible for sparking, thanks to the smooth movement of the magnet over the coil.

In other words, when the magnet fails to pass over the coil at the right time, most mowers fail to start. That’s why lawn mowers have a flywheel key to ensure perfect alignment between the various components.

It’s a small metal rectangle that prevents damage to the riding mower engine. Naturally, you should check for signs of wear and tear and replace the flywheel key if it’s broken.

For instance, when you hit a large rock or object while mowing, it may break or shear the flywheel key, following which the engine stops. Meaning, if something like this happened to you recently, it would be wise to install a new flywheel key and check for internal damage surrounding the engine.

Cylinder Compression

At times, the problem might be staring you right in the face, but you may still miss it. Hence, it’s a good idea to remember the basics and check the compression to get the mower started.

People often fill their mowers with too much oil, so drain some out if the oil level is more than the maximum limit. Then, take the compression reading with a test gauge, ensuring that the fuel is mixing with the cylinder.

A compression reading of over 40 PSI is ideal, but if it falls below this level, the test confirms that there’s a compression problem. You’ll need a licensed technician to fix the issue in such a scenario and get the lawn mower running quickly.

Final Words

If you were wondering – “why is my lawn mower turning over but not starting?” – before reading this guide, well, now you know.

Follow all the procedures we have mentioned above, and your lawn mower should be ready for use quickly. That said, if you’re confused and can’t locate the issue, don’t hesitate to call an expert to get it fixed.

Also, regular maintenance goes a long way to ensure that all the parts are in working condition. So, take care of your lawn mower by dusting the cobwebs, changing the filters, and monitoring the fuel mixture, among other things, to keep issues to a minimum.