You are ready to mow your lawn, you start your lawnmower, and it stops for a few seconds later, or it works with a couple of minutes and dies. You restart it and it stops again, and you sigh… it’s one of those days. If your lawnmower keeps stopping it might be as simples as checking your fuel cap is not clogged, changing your sparkplug, cleaning your airfilter or unblocking your muffler. But it can sometimes be something more complex like a damaged carburettor and you need a professional to service it. Many of these lawnmower problems are easy to troubleshoot, diagnose and fix. If you have time, patience, and some mechanical skills, you can do it yourself. Don’t worry! Below you will find a list of the most common problems to help you with your lawn mower troubleshooting. Why does my lawn mower keep stopping? Your lawn mower might keep shutting off because as something simple as something is clogged up, you need a new spark plug, or you need to add new fuel. Of course, the first thing you should look at is your owners manual. As it contains information unique to your lawnmower. But this guide goes through some of the most common basic troubleshooting steps from the easiest to the worst problems. The idea is for you to use it as a guide to check your lawnmower problems and at the same time as a checklist to troubleshoot your lawnmower. 1. Check if your lawnmower has a clogged fuel cap vent If your lawn mower keeps cutting out, check you fuel cap. Fuel caps have one or more small vents to let the air in as the fuel level is going down inside the fuel tank. This air compensates the inner pressure with the outside pressure and lets the fuel flow. If the fuel cap is clogged, fuel will be unable to reach the engine, making it stop. One quick way to test your lawnmower’s fuel cap is to loosen it, making sure that air is allowed into the tank. Now turn on your lawnmower. If it keeps running, the problem is the fuel cap. You can try to clean it or just replace it. 2. Grass blockage can cause your mower to stop – Check the lower end of your mower If your lawnmower is not very powerful, a build-up of grass clippings underneath the mower can make it difficult to mow and ultimately cause your mower to stop. Carefully inspect the underside of your lawnmower and check for clipping build-ups. Try to remove all lumps of grass, clean the area and try again. You can also try to adjust the cutting height to a higher setting to reduce problems with grass build up. 3. Blunt blades and long grass can make your lawn mower stop Blunt, unsharpened or damaged blades could also cause the lawn mower shut off while mowing. This is because blunt blades will need more power to cut through the same amount of grass as sharp blades. If the blades are not sharp enough, they will tear the grass instead of cutting it. This grass could stick to the blades, preventing the correct functioning of the machine. 4. An exhaust blockage can cause lawn mower problems This is a long shot but it’s very easy to check. Inspect your mower’s exhaust pipe and muffler. If it’s clogged with dirt or debris, the exhaust fumes won’t be able to leave the engine freely and will stop the engine. Wasp nests are more common than you think! 5. Your lawnmower problem could be due to leaking oil If your lawnmower’s oil level is low, it’s dangerous to your lawnmower’s engine. It could also be the reason why your lawnmower keeps stalling out. Before further testing, top your mower’s engine oil according to the user’s manual, don’t overfill it and try again. Your lawnmower should always run with the right amount of oil. Once you know there is the right amount in there, you need to look for what part of the engine is leaking. Unfortunately, there are a few places where the leak could be coming from, and it could be coming from more than one spot! To start to work out where the leak is coming from, you need to wipe the whole engine over with a rag and a brush to get rid of any oil and dirt that has built up on the outside. Once it is clean, it make it easier for you to see what is going on. Then, run the engine for a few minutes as often seals will only leak during use or immediately after. If there are leaks, hopefully this will help you identify them. The most obvious thing to check with a lawnmower leak is whether the seals, o-rings and gaskets are worn. The first one to check is the lower bearing ring seal (aka oil seal). This is underneath the engine and the crankshaft that spines the mower blade goes through it. If the lower bearing ring seal is leaking, then you will find an oil leak directly underneath your engine. If your valve gasket needs replacing you might see a build up of oil around the valve chamber where the cover attaches. To work out if that is the source of your leak, clean it up, and run the engine for a few minutes. Then if you see oil appearing again in that area, then you probably have found the culprit! 6. Too much oil can cause a lawn mower to stall Excess of oil in your mower’s oil reservoir may drown the engine and make it stop. If there is too much oil in your mower’s reservoir, you are probably going to see that your mower is smoking, leaking oil, or even blowing blue smoke. In this case, blue smoke coming out of the engine is a result of the excessive oil burnt by the engine. If you realize that