How To Fix A Lawnmower That Will Not Start

The two basic requirements that allow a lawnmower’s engine to startup are fuel and a spark. If you are experiencing fuel starvations (when fuel is not getting to your engine), or if you are not getting a spark at the plug, your engine will not be able to startup. 

Bad compression can also be a reason for experiencing difficulty while trying to start the lawnmower’s engine. If you pack the lawnmower away for the winter with fuel still in the tank, the seals, valves, and pumps in the lawnmower’s carburetor can become blocked up with varnish deposits. Along with this, dirt and dust can get collected and end up blocking the fuel system or clog filters. 

broken lawnmower fixes

Before You Start Troubleshooting On Your Mower You Should:

  • Remember that gasoline and oil are flammable substances. 

Proceed with caution when working with your mower. You should first start by removing any sources of ignition. This includes cigarettes, naked flames, sparks, stoves, or other hot objects that are in the same area that you intend on working on the tank or fuel lines. 

  • Make sure the spark lead is disconnected.

Be sure to do this if you need to remove any clumps of grass that may be jammed under the deck.

  • Ensure the carburetor side of the engine is kept upright.

This is to avoid the oils in the mower from spilling, as this is likely to happen if left on its side.

  • Drain the tank if you plan on putting the lawnmower on its side.

This can be avoided if there is a small amount of gas in the tank, or if you do not think that it will reach the tank cap. However, if you are unsure of this then it would be best to just drain the tank. Another trick is to open the cap and then place a plastic bag over the opening and then put the cap back on.

  • Check the level of the oil.

You are likely to cause premature engine wear if the oil level is low. Added to this, an engine can seize quickly if there is no oil present in the lawnmower. 

Top Reasons Lawn Mower Not Starting — Lawn Mower Troubleshooting

Checking On The Oil Level Of Your Lawnmower:

Before starting the process of troubleshooting, you should make sure that the oil level in the lawnmower is deemed acceptable. You can do this by:

  1. Move the lawnmower to a surface that is level. 
  2. Remove the dipstick and wipe it clean.
  3. Place it back in the lawnmower and then remove it again.
  4. Check to see where the marking is. If it is relatively low, top it up to the necessary level. 

You should make a mental note that the oil in the tank should be changed after every 25 to 50 hours of run time or as advised in your engine manual. 

How to check your lawn mower's oil level

How To Start A Lawnmower With A Small Engine:

  1. Set the throttle to high revs or the choke position. Turn it on if the engine has a manual choke. 
  2. If the primer button is lifted, you should press it around 8 times. 
  3. Quickly pull the starter rope. Try not to yank it too hard. 
  4. Allow the engine to reach top speed before you begin to use it. Turn it off after five seconds if your engine has a manual choke. 
  5. Do not turn the manual back on again if you intend to start a hot engine.

Tips To How To Get Your Lawnmower Started:

  • Make sure you are using fresh gas. Do not use old gasoline or petrol as it can cause difficulty when trying to start your lawnmower’s engine. Added to this, you should make sure that there is enough fuel in the gas tank as well as check that the vent in the tank cap is not blocked.
  • Check to see that the spark lead is securely attached to the plug, and that the plug is tightly screwed in. If not, you can resolve this by replacing the spark plug with a new one. 
  • See that the ‘dead man’s handle’ control found on the mower is held fully against the mower handle while starting. 
  • The choke should be turned on if there is a manual choke fitted on the lawnmower. However, do not turn the choke on if the engine has been running in the last five minutes or so.
  • If a primer bulb is fitted, make sure to press it approximately five times. If the lawnmower runs out of gas while you are cutting grass, you will need to repeat this step as the mower will need to be primed again. 
  • Check to make sure that the air filter is not dirty. Replace the dirty paper filter or wash and dry the foam type air filter. 
  • Look to see if the cable connecting the ‘dead man’s handle’ is not snapped or damaged. This handle can be located on the frame next to the engine.
  • The carburetor should be properly screwed on or bolted to the engine. You should check to see that this is correct.
  • There should be no water, under any circumstances, lodged at the bottom of the gas tank.
  • If the starter cord is hard to pull, this could be an indication that there are clumps of grass clippings clogging the underside of the deck. As a result, this can jam the blades. However, before you attempt to move the blade to remove the clippings, you need to disconnect the spark lead. 
  • Some newer push mowers are operated by starter motors and batteries. If you have a newer push lawnmower, you should check to see that the battery voltage is over 12 volts as anything lower will not start the engine.

How Do You Start A Lawnmower With Old Gas?

  • Clean out the lawnmower’s gas tank

Although, it is recommended to drain the lawnmower’s gas tank before it sits for a long period of time without any use. However, most people do not do this. The result of not draining the gas tank causes residue build-up. If this occurs, you should refer to your lawnmower’s manual for information on how to remove this build-up from the fuel tank effectively, as well as for service procedures.  Or see our guide on this problem.

  • Remove any remaining gas from the tank

As soon as the build-up has been cleaned out, gather all the old gasoline and put it in a container to dispose of it properly. This can be done by running a siphon hose from the gas tank to the container and then pumping the bulb a few times. In doing this, you are moving the gas from the fuel tank and draining it into the container, which thereby cleans out the lawnmower’s fuel tank. 

  • The spark plug should be checked

If your lawnmower still is not working after you have cleaned out the fuel tank and adding new gasoline to the mower, you should make sure that your spark plug is working.  There is a large possibility that the spark plug wire will become loose after being stored for long periods at a time. 

  • Do not flood the carburetor

A common problem found when trying to restart a lawnmower that has been stored in that the carburetor gets flooded. Be sure to note the smells and sounds of the lawnmower while you are trying to start it. A strong gasoline smell could mean that the carburetor has been flooded, and as a result, the lawnmower will not start. In this case, you should wait a few minutes before you try to start the mower again. 

How to fix a lawn mower that won't start after storage

How Do You Dispose Of Your Lawnmower’s Oil?

When cleaning out the oil in your mower, be sure to collect in a bottle-like container that screws shut. This is to prevent any spilling. Your local mechanic or oil change shop should usually take your used motor oil to dispose of properly. However, if this is not possible, there may be disposal programs for motor oil at your local dump. 

If smoke is coming out of your mower, this could be a sign that the oil needs to be checked and changed. However, a lawnmower that will not start obviously will not smoke. Nonetheless, this is a good sign to look out for as it will allow you to stay on top of your lawnmower maintenance. Added to this, smoke coming from a mower could show that there is a leak somewhere. The leak causes the oil to burn when it lands on hot surfaces such as hot metal. Along with this, smoke can also indicate that there is not enough oil in the lawnmower. Not enough oil has the potential to cause permanent damage to the engine of the mower. 

What Is My Opinion On No-Hassle Gas?

One form of no-hassle gas is a product called TruFuel and it is available in most hardware stores. Known to be “old school” gasoline that has no added ethanol. What is so great about this product is that you do not have to add any fuel stabilizers. It runs clean and can sit in storage all winter and will still start up very easily. 

However, it is more expensive than regular gas. Nonetheless, when you weigh in that while using no-hassle gas you will not need to pay to replace your lawnmower or carburetor every few years. 

So after reading my post on how to start a lawnmower that won’t start and you decide that it’s easier just to buy a new one, then be sure to check out my post on the best mowers that are under $300.