The most common issues of your lawn mower not operating correctly
Troubleshoot your small engine FAQ:
Why wont my lawnmower start? Remember the 3 basic principles of “spark, fuel and compression”. First we are checking if there is gas in the gas tank. We may have adequate gas in the tank but gas can be stale from sitting over the off season. Ensure you have fresh gas in the gas tank before moving onto the next step. Secondly, we will check if we have spark at the spark plug. If at this point we have not determined the cause of our lawn mower not starting, we go to the third step which is to check for compression.
My lawn mower wants to start but sputters and dies. You could have a situation where it’s just run out of gas and is getting just enough gas to pop but not start so check your gas tank gas level. It would also be a spark plug that is going bad, usually not likely. You might have an overheating ignition coil that’s going bad.
My lawn mower starts and runs for several minutes then dies. Both scenarios are equally likely. You may have a fuel starvation situation whereby the gas tank vent is not working properly and thus the gas tank is being drawn under a vacuum. This is easy to test for; loosen or remove the gas tank cap and see if the lawn mower starts and runs longer then the experienced interval of it running and dying. The second situation would be an ignition coil that is going bad. In this situation the engine is running long enough to warm up the ignition coil at which point the ignition coil starts cutting out and no longer delivering a consistent spark for the engine to run.
I go to pull the starting rope on my lawn mower and it pulls extremely hard. Your engine brake cable could have broken and now the engine brake is always engaged and thus resulting in this condition. It may also be the flywheel key is sheared and now the ignition timing is off and resulting in out of time ignition and misfiring. Thirdly, and least likely, is the mower deck so clogged with grass clippings the blade has a difficult time rotating.
When I pull the rope to start my lawn mower it rips the rope handle out of my hand. 9 out of 10 times you have a sheared flywheel key resulting in an out of time ignition cycle. In this case, remove the engine cover, and check the flywheel key condition.
My lawn mower starts and runs but surges up and down. It could be starving for gas as the gas tank level is too low to deliver the proper amount of gas to the carburetor. Your carburetor may have dirty, clogged fuel jets and needs cleaning. Lastly, your governor may be out of adjustment, highly unlikely.
My lawn mower is puffing white smoke when I go to start it. Your lawn mower is flooded from a carburetor float needle seat gone bad and is now allowing gas to overflow the carburetor and possibly overflowing into the crankcase of your engine. The auto-choke on your lawn mower engine has gone bad and is no longer turning the choke off as intended once the engine is warming up.
My lawnmower starts and runs but sounds like it’s running way faster than normal! Your governor is not set correctly. You will need to set the governor using the proper procedure for your engine.
My lawn mower starts and runs but sounds like it’s running slower than usual. If your lawnmower has a throttle cable, perhaps your throttle cable isn’t correctly set and needs adjusting. Secondly, your governor may need adjusting. You will need to set the governor using the proper procedure for your engine.
My lawn mower starts and runs but is belching blue smoke from the muffler. Your engine is burning oil. Your engine oil level may be overfilled. Check the engine oil level via the engine oil dipstick. If it’s overfilled, you will need to remove some of the oil until the oil level is at the “full” mark and not overfilled past the “full” mark. Please note that after the engine has run, you need to let it sit a few minutes for the engine oil to settle down in the engine crankcase again for an accurate oil level check. On a more serious note, if your engines oil level is normal and its belching blue smoke, you have a bad engine; meaning your lawnmower engine has internal worn parts that are resulting in it allowing oil into the combustion chamber and that oil is part of the gas air mixture as the engine runs and is resulting in blue smoke coming from the muffler. Your lawn mower engine needs to be rebuilt or overhauled.
My lawnmower starts, runs but vibrates and shakes while it runs. Your lawnmower’s blade is bent or out of balance. Your blade(s) need checking for damage and need to be rebalanced. Secondly, you may have hit an object like a rock or stump and now your blade, blade adapter or worse the crankshaft is bent resulting in the lawn mower shaking and vibrating. You will need to have these items checked to determine what is causing this.
My lawnmower veers off to the left or to the right as I’m mowing the lawn. This is always always caused by the same issue; the wheel height adjusters are bent. You will need to determine which ones are bent and take the wheels off and bend the wheel mount bracket back to a straight, neutral position.
My lawnmower starts and runs but is not discharging grass clippings from the side discharge chute. Make sure the side discharge removable chute is in place. May also be that the side discharge chute opening is clogged with grass clippings. With the lawn mower engine stopped, check if the discharge chute opening is obstructed with grass clippings.