Bad gasoline could be the cause of a sputtering lawn mower. If your lawn mower refuses to start or is hesitating, there is a very good chance that a bad gasoline may be the fault or a bad spark plug. If you have checked to see that the spark plug is in good working condition the next item to troubleshoot is the state of the gasoline.
Sometimes stagnant gasoline that has sat in the tank for long periods (especially all through winter) will separate and deposit gasoline at the bottom of the tank.
By doing so, poor combustion fuel floats at the top of the tank and can find its way into the fuel-sensitive carburetor. This will lead to clogging of the fuel filters and subsequent poor engine performance.
If gasoline has sat in the fuel tank for a long time, adding fresh gasoline to it is a very bad idea, because the old gas deposits break loose when new gasoline is added.
An important measure to take very season is to ensure that you drain the gas tank from every atom of gasoline after the last use. Doing this will prevent poor preforming engines next spring and improve the shelve life of the tank.
Follow the steps outlined below to completely drain the lawn mower tank of gasoline after the last use:
Park the lawn mower on a flat surface after the last use or alternatively set it on a set of saw horses to allow access to the underside. Please ensure that you avoid tipping the lawn mower on it side at all cost.
If you do, oil can run from the reservoir to other parts of the motor. Also apply the parking brakes of the lawn mower to keep it stationary.
Next, disconnect the spark plug by pulling the spark plug wire from the spark plug cap. This is a precautionary measure to avoid hazards.
If your mower comes with a fuel line that runs from the gas tank to the carburetor then all you need do is set a collecting plastic container beneath the tank.
Just disconnect the fuel line from the carburetor and allow the old gasoline drain out into the collecting container.
If your mower doesn’t come with a fuel connector, you will have to make use of a gasoline siphon to drain out the gasoline.
By placing the clear end of the siphon in a jug, inset the brass siphon end into the lawn mower and shake vigorously up, down and sideways.
This vigorous shake action will start the siphoning process. You should see the gasoline flow seamlessly from the lawn mower tank to the collecting jug.
Repeat step 4, over and over again until most of the gasoline has been drain off.
Once the siphoning action has removed most of the gasoline, remove the brass end of the siphon from the tank. No matter how good you are at setting up a proper siphon pipe, there will still be gasoline residues within.
In this case use rags to soak up any remaining gas from the bottom of the tank.
Now, add a little fresh gasoline into the tank to slosh it around. The fresh gasoline will mix-up with any old residue still left in the tank. Drain off this new mixture of both fresh and old gasoline into a plastic container.
Ensure you have completely drained off the old gasoline from the tank. Then allow drying for a couple of minutes before reattaching the fuel line and spark plug wire.
Check to see that the air filters are not clogged. If they are clogged, clean them up or purchase a replacement.
Check also that the oil reservoir is full. Then pull the mower cord to start. Let it run in idle mode until it quits. This step is necessary to remove left-over gasoline from the carburetor.
Finally, place the mower on the ground from the supports and refill the tank with fresh clean gasoline. Start up the lawn mower again. You may experience some initial sputtering for a while until the mower burns through the fresh gas.