If you are struggling to get your lawnmower started it could be down to a variety of reasons. In most cases, you will find that a four-stroke lawnmower engine won’t start due to issues with the gas or carburetor. Other common issues include problems with the starter rope, a lack of oil, or possibly faulty wiring and connections.
Thankfully, most lawnmower starting issues are related to gas or the carburetor, making it easier to identify the problem and fix it accordingly.
You will also find that lawnmower starter problems often arise during winter due to the engine being stored for prolonged periods. This often causes parts of the carburetor to accumulate varnish deposits when fuel is left in the tank.
The problem also may have occurred during summer, where dirt and dust build up and case blockages in filters or the fuel system.
Add New Gas
Old gas is often a cause of starter problems with lawnmowers. This is especially true for gas high in ethanol as this may increase the chances of moisture in the fuel, leading to corrosion. The fuel also leaves deposits such as varnish or gum over time, clogging the engine and making it difficult for components to operate.
So, try carefully removing the old gas from the engine, especially if it has been sitting for a while unused. Also, try using fuel stabilizers for the new gas to avoid similar issues over the upcoming winter.
Spark Plug Issues
There is a chance the issue is caused by the spark plug being too wet. When this occurs, the engine has no chance of starting, so you want to address this problem as soon as possible. If you discover a wet spark plug then you need a carburetor cleaner to thoroughly clean it.
While an air compressor may seem like the ideal cleaning solution, the issue arises from the oil residue, which is why a good cleaning solvent is needed.
After this, allow the spark to completely dry before putting it back in and seeing if it works. You might need to pull several times to get it working.
Other spark plug fixes include making sure it is securely attached to the plug and that the plug itself is screwed firmly in place. It may also be a good idea to replace the spark plug if it appears too worn and covered in thick residue. If any models are known for having issues with their spark plugs, this is something you should consider when choosing a new lawn mower. In most cases, it is not a major issue and can sometimes be the result of leaving the machine sitting out in the wet unattended for long periods.
Inspecting the Carburetor Bowl
A common problem with lawnmowers if the engine struggles to get gas because the fuel filter is plugged, while similar issues happen when a carburetor inlet needle is lodged in. To check the fuel filter simply remove the fuel line on the carburetor and look for gas to pour out from the line.
If there is no gas running out then remove the fuel line before removing the fuel filter inlet. Should gas pour at this stage then it means the fuel filter is clogged, in which case you need to replace it. If there is still no gas at this stage, then it is likely the fuel line is plugged or kinked.
When there is gas entering the carburetor then you want to inspect the carburetor bowl and look for fuel here. This can be done by removing the fuel line using a c-clamp and then removing the bowl – if there is nothing inside then the problem is the stuck inlet needle.
Replacing the Inlet Needle
If the above problem is caused by a lodged carburetor inlet needle then you can easily replace it. Remove the float pin and wait for the inlet needle, float, and spring to fall out and then remove the rubber seat. Simply reverse these steps with a new inlet needle, float, and spring.
Checking the Rest of the Carburetor
Anyone checking the carburetor that finds either of the above problems can easily replace the parts – but its worth inspecting the rest of the carburetor for signs of more significant damage.
For instance, look inside the carburetor and check for signs of white powder deposits. This indicates corrosion which essentially means the carburetor can’t be fixed and needs to be replaced.
Also, look to see how tightly attached the carburetor is to the engine. It should be firmly in place, so try tightening any screws or bolts if it feels too loose.
Starter Cord Problems
Some lawnmowers cannot start due to the starter cord. Whether it’s too hard to pull, struggles to wind up, or constantly slips, there are ways to fix starter cord problems on the mower.
Start by checking for clumps of grass. Moist grass or moss build-ups often go unnoticed on the underside of the mower and make it difficult for the blade to rotate. Check the base of the mower to see if there is a build up and remove it carefully. Make sure the spark plug is removed when doing this to avoid any possible accidents.
Another thing causing issues with the starter cord is the flywheel brake. This brake works to stop the engine when you use the dead man’s handle, so there is a chance this has become lodged in place or that the wire powering the brake is broken, meaning the engine can’t turn.
To fix this you need to check and possibly replace the brake or wiring, although dislodging it may also work. You can inspect this part of the mower by taking off the cowling at the top.
Lawnmower engines, like any combustion engine, require engine oil to lubricate the moving components and keep everything in working condition. A lack of engine oil may be the cause of the engine troubles, as little or no oil causes seizing in the engine.
Always check this when the engine is cold and make sure the mower is placed on a flat surface to get an accurate reading.
There should be dipstick attached to the oil cap on the crankcase at the lower end of the engine, which is where the oil is stored, so unscrew the cap and clean the stick. Insert the stick and remove it to check the oil levels – there should be a marker on the stick showing the minimum and maximum levels.
It’s recommended to change oil every 50 hours of use, so consider doing an oil change to keep things operating. Avoid running too low as it will impair functionality and possibly lead to long-term engine damage.