Before Working on Your Mower

Remember to always ensure the mower is off and the spark plug wire is disconnected before inspecting or working on any part of the engine. To safely remove the spark plug cap firmly grasp the cap itself and pull it straight off the spark plug in a straight line. Avoid pulling on the wire itself to prevent damage, pull on the metal cap. Secure it away from the spark plug.  

 

1. Check the Fuel Level

*Please refer to your User Manual for specific instructions on your model

Remove the fuel cap and look in the fuel tank and see if there's fuel, if not add at least half a tank and try start it again. Refer to your User Manual for recommended fill capacity. 

2. Check for a Primer Bulb. 

If your mower has a Primer Bulb, ensure you are priming it correctly (when the engine is cold) according to your owner's manual. 

If your mower does not have a Primer bulb, ensure you are starting it correctly as directed by your owner's manual. 

3. Check for Bad Gas (Most Common Cause if Your Mower Won't Start after Winter Storage)

Your engine needs fuel to run. Fuel can degrade over time (especially if not treated with a fuel stabilizer over the winter) and can cause starting problems or make the engine run poorly. Gas can go bad in as little as a month or two. When it goes bad it can attract water and turn into a varnish-like substance that clogs fuel lines and the carburetor.

How to Check: Does the gas look murky, or does it smell stale or like varnish? How old is it, is it from last season? Is there any dirt and debris in the tank? Even small bits of dirt and debris can clog the tiny holes in the fuel system like the carburetor jets.

If the gas is determined to be old and stale it needs to be drained and refilled with fresh gas. Use a fuel siphon (look for a manual siphon pump, it will come with a hand squeeze bulb and two lengths of tube attached). Drain the old fuel into an approved gas can and replace with fresh gasoline. Then try to start the mower again. If the mower still does not start the stale fuel may have clogged something in the fuel lines or carburetor but first try the remainder of the guide before moving to troubleshooting that issue.

Materials Needed: Siphon, fresh gasoline and an approved gasoline container to drain old gas into.

If your mower still does not start and your fuel is over 3 months old please see our guide here

4. Check the Oil Level

Your engine needs oil to run smoothly and prevent damage to the engine. 

*Please refer to your User Manual for specific instructions on your model

How to Check: Use the dipstick to check the level. With the mower on a level surface unscrew the dipstick. Then reinsert the dipstick WITHOUT screwing it back in. Remove it and examine the oil level. If the level is at or below the minimum oil level marked on the dipstick refill to the maximum oil level mark.  If there is no oil or it is low fill according to the User Manual. 

5. Check the Battery (Electric Start Mowers Only)

If your mower is equipped with an electric start ensure the battery is charged. If your battery has a fuel gauge on the back charge it until it reads full then try start your mower again. 

6. Check the Air Filter

The air filter cleans the air before it mixes with fuel in the carburetor. If the air filter is clogged with dirt, grass, or debris, it restricts airflow which can prevent the engine from starting or cause it to smoke.

*Please refer to your User Manual for specific instructions on your model

How to Check: The air filter is typically in a plastic housing on the side of the engine, held on by a plastic nut. Loosen the nut to remove the cover and look at the filter. If it looks dirty or clogged, it needs to be cleaned or replaced. If you have a foam filter you can follow these steps to clean it: 

1. Loosen the nut and remove the air filter cover. Remove the air filter housing and elements and inspect for cleanliness. 
2. Replace filter if it is damaged.
3. If it is not damaged clean the foam air filter with soap and water and let dry. 
4. Pour a few tablespoons of fresh motor oil on the foam element and work it in thoroughly. 
5. Gently squeeze and then pat out all excess oil and reinstall. 

Materials Needed: A new air filter if replacing the old one and a foam filter, warm water, detergent, and fresh engine oil to clean the existing filter.

7. Check for Debris Under the Mower Deck

Sometimes, especially when cutting wet or very long grass, clumps of grass clippings or other debris can get packed under the mower deck and jam the blade. If the blade is stuck, it can make the pull cord very hard or impossible to pull and prevent the engine from turning over and starting.

*Please refer to your Owner's Manual for specific instructions on your model

How to Check: Ensure the spark plug wire is disconnected! Safely tip the mower on its side (tipping with the carburetor & air filter side up is recommended to avoid splashing oil all over the mower). Look under the deck for packed grass or objects wrapped around the blade or crankshaft.

Materials Needed: Gloves and a scraping tool (ideally a plastic putty knife (not metal) so you don't scratch the paint off the deck's underside if grass is built up.

8. Check the Fuel Cap Vent

The fuel cap usually has a small vent that allows air into the tank as fuel is used. If this vent gets clogged, a vacuum can form in the tank, preventing fuel from flowing to the engine, and the mower might start but then die after a few minutes.

How to Check: Try removing the fuel cap and then try to start the mower (Be careful to keep grass clippings and dirt out of the fuel tank while the cap is off). If it runs without dying the fuel cap may need to be replaced. 

9. Check the Spark Plug

The spark plug creates a spark that ignites the mixture of fuel and air in the engine. If the plug is dirty, damaged, wet with fuel (flooded), or the ignition coil with spark plug boot is loose, it won't provide a strong enough spark to start the engine.

How to Check: Make sure the spark plug boot is securely attached to the top of the spark plug. If it was loose attach it then try to start the mower, this may have been your issue. If it was securely attached and ‘pops’ off with a little tug continue to troubleshoot.

Pull the spark plug boot off. Use the included spark plug wrench to check if the spark plug is threaded directly into the cylinder head creating a gas-tight seal. 

Use the included spark plug wrench to carefully unscrew the ignition coil. Look at the tip of the plug. Is it covered in an excess of black, sooty buildup? Is it wet with gas or oil? Is there a gap between the plug and the bent arm or is the top of the plug bent down to close the gap? The space between the metal tip and the bent arm (the gap) should be clean and clear and you should easily be able to see the gap with your eye. You can try cleaning the plug with a wire brush or sandpaper and some carburetor cleaner, especially if it's wet or dirty. Let it dry completely if it was wet. Then reinstall according to your Owner's Manual.

Materials Needed: Spark plug wrench (should have come with your unit), ratchet, towel or rags, carburetor cleaner, wire brush or sandpaper. Possibly a new spark plug.