Angie's LIST Guide to
Lawn mower repair

The average suburban lawn mower is a true workhorse, but you might not be maintaining it as well as you should. Here are some practical tips on troubleshooting common problems, how to make some lawn mower repairs yourself and how to maintain your mower so it keeps performing well year after year.

Lawn mower won't start

There are three main reasons why a lawn mower will not start. This can be due to fuel issues, battery related or sparking problems. Conduct a few troubleshooting methods to narrow down these problems, which can often be corrected at home.

Fuel issues

  • Ethanol-based fuel will gel up and clog the carburetor if you fail to empty it at the end of each mowing season.
  • Fuel that is currently in the lawn mower may not be properly mixed or otherwise bad. Siphon out the old fuel and replace it with fresh fuel.
  • If the lawn mower has new fuel, check the carburetor to ensure that fuel is properly flowing to it. All fuel lines should be checked to make sure they are not loose, kinked or clogged.
  • The fuel filter is an important component to the proper operation of the lawn mower. If the fuel filter is dirty, missing or clogged, the proper flow of fuel can be disrupted.
  • The float within the carburetor can sometimes become stuck in the lawn mower. Slightly tapping on the carburetor can free the float and allow the fuel within the mower to flow better.

Battery-related problems

  • When a lawn mower has a spark and is filled with fresh fuel and rolls over, it may mean that the battery needs charging.
  • Battery cables can loosen up while sitting or from jarring that takes place during use. Make sure all battery cables are secure and tightened properly.
  • After sitting for long periods of time, a battery may not want to hold a charge. This can be fixed by replacing the battery in the lawn mower.

Spark problems

Changing lawn mower spark plug
Spark plugs are inexpensive and pros recommend replacing them every year or two. (Photo by Katie Jacewicz)
  • Problems that occur after sitting during cold weather seasons may signal a situation in which the spark plug wire has not been properly attached as needed.
  • If the motor of the lawn mower does not turn over, this can be a sign of a bad spark plug. Remove the spark plug, and inspect it for debris or improper gapping. Replacing the spark plug when using it for the first time of the season can help this problem. Refer to the owner’s manual to locate the right size spark plug needed and the recommended gapping of the spark plug for their specific lawn mower model.
  • If spark is present within the motor of the lawn mower, this can mean that the mower needs new points or a new ignition module. This is determined again by the type and age of the lawn mower model.

For more information read: Help! My Lawn Mower Won't Start

Common lawn mower problems

Mower loses power: If a lawn mower is losing power while in use, this can mean that there is either bad gas in the mower or the air filter is dirty and needs to be replaced.

Lawn mower is overheating: Many lawn mower models are equipped with cooling fins and engine shrouds. If these components fill up with dirt, grass clippings and other debris, it can cause the mower to quickly overheat. Sensors within the mower will be signaled to stop the mower from running or from being started.

Removing lawn mower blade
Use a socket wrench to remove the blade from your lawn mower. (Photo courtesy of Katie Jacewicz)

Won’t cut right: Blades have a tendency to become duller with each use. Nicks in the blades that occur when hitting rocks, large stumps or other hard objects can greatly affect the cut. Remove the spark plug to prevent the mower from accidentally starting, then remove the blades. They can then be sharpened, but consider hiring a professional for this dangerous task.

Learn how a tuneup can keep your lawn mower running: Why You Should Get A Lawn Mower Tuneup

Lawn mower maintenance

Simple, routine maintenance can help extend the life of any lawn mower.

  • When storing the lawn mower for longer than a few weeks, siphon out the fuel.
  • Empty out any baggers attached to the lawn mower after each use.
  • Grass buildup and debris should be removed from the underside of the machine, blades and other areas of the lawn mower to prevent damage to the lawn mower.
  • Batteries should be removed if they are used within the lawn mower before storing the machine. This can help to prevent freezing and damage to the cells within the battery.
  • If you do not have the skills necessary to repair or maintain a lawn mower, enlist the help of a professional. This is especially important when working with the cutting blades and internal combustion components of the machine.

For more see: Why Old Fuel Is Bad For Your Lawn Mower


engine runs good, but blowing blue smoke from the front. probably a gasket. how much to fix.

I have a Troy bilt tiller that has a Briggs and Stratton 5 HP motor on it. When I pull it to crank it, it won't even hit or crank and I checked the spark plug and it is firing and gas is going in the motor like it is supposed to what could be the problem? Can u please help?

Does it have compression?

It stops after working 2 or 3 minutes. It was storaged for the all winter

I can't get my lawn tractor to move forward or backwards even if I put it in free wheel. Any suggestions it's a craftsman 1000

I have a problem with my mower (walk behind) when I start it , its run then two minites it dies. Then when I go to start it, I pull and pull and nothing. I notices a connection where there is a contact, I think that is a maganto, could that be the culpert. It is a Craftman mower and I wonder if you have any think on that.

It is brand new, that do not need priming

it has a pull starter and for some reason is not engaging the engine. Apparently the mechanism that turns over the engine is not being turned when you pull the starter rope. I have remove most of the bolts involved but cannot reach the flywheel to fix it.

For gas engines add to the gas an ethanol treatment unless all the gas will be used in the month.

Always buy premium gas to offset ethanol deterioration, it keeps up the compression but does not cure the water issue of old ethanol/gas.

BUY "Mechanic in a Bottle" to start equipment that won't fire, and to tune-up running gas equipment.....

Above available at Home Depot and made my lawn mower and weed whacker run much better. Old gas sucks in water which destroys motors and parts used to run the motor.

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