How frustrating it is! You just finished filling up the gas tank and are ready to work on your lawns. But your lawn mower starts and then dies before you even get to mow. That’s a common issue many homeowners might have dealt with during the mowing season. Let’s get through this article to find out the primary causes and step-by-step fixes to end this headache.
Common Causes Your Mower Starts Then Dies
Clogged Carburetor
A carburetor is essential to power your lawn mower’s engine by mixing the air and fuel in the proper proportion. Over time, the dirt, old fuel or even moisture gums up the carburetor, restricting the fuel flow and then causing your engine to start but stall immediately. This matter would be even worse if you just take out your mower that has been sitting for a long time.
How to Fix:
- Turn off the mower and disconnect the spark plugs in case it starts accidentally.
- Locate the carburetor near the engine or underneath the air filter.
- Inspect the carburetor for dirt and debris.
- Drain the carburetor bowl and use a spray carburetor cleaner to remove any visible grime.
- Remove or rebuild your carburetor if necessary.
- Reassemble the carburetor by reattaching the air filter and covers that you removed.
- Reconnect the spark plug and turn on the mower to see if it runs smoothly.
Here is an article you might enjoy: How to Clean a Honda Lawn Mower Carburetor?
Old Fuel
Old or stale fuel is another culprit for why your lawn mower starts and stops just seconds after being primed. Fuel can degrade if it has been sitting in the mower tank for too long. The varnish and deposits produced can clog the fuel system and prevent efficient combustion. It is recommended you replace the fuel every one to two months.
How to Fix:
- Drain all old fuel from the tank by using a siphon pump and then dispose of the old fuel properly.
- Inspect the fuel filter and replace it if it is clogged.
- Refill the tank with fresh fuel, ideally with low ethanol content.
- Add a fuel stabilizer to protect your fuel from degradation, especially when you store the mower for a while.
Dirty Air Filter
A dirty or clogged air filter is also to blame. The major function of an air filter is to keep dirt and debris out of the engine. When the air filter gets clogged with grass clippings or dirt, the airflow can be restricted, which may account for why your mower starts and dies shortly afterward.
How to Fix:
- Locate the air filter, which is usually inside a plastic housing on the side or top of the engine.
- Inspect the air filter for dirt and grass and decide whether to clean or replace it.
- Rinse your foam or sponge-style air filter under water with mild soap or use compressed air to blow out dirt.
- Gently tap your filter to remove loose dirt for a paper-based air filter.
- Reassemble the air filter housing and make sure the air filter is dry and seated.
Faulty Spark Plugs
A fouled or worn-out spark plug can lead to weak or intermittent sparking. Besides, a failing spark coil or a compromised spark plug wire can cut power instantly, even though there is a spark from a start. All these can explain why your mower starts but dies right away.
How to Fix:
- Locate and remove the spark plug using a wrench. Replace the worn or damaged spark plugs.
- Inspect the spark plug for carbon build-up, oil deposits, or cracks and corrosion. Clean the dirty spark plug and replace a damaged one.
- Use a wire brush or sandpaper to clean your spark plugs to make sure the electrode is free of carbon buildup.
- Check and measure the gap between the spark plug electrodes using a feeler gauge to ensure it matches the manufacturer’s specifications.
- Reinstall the spark plug and reconnect the spark plug wire after cleaning or replacement. Then, start your mower to see if it runs smoothly.
Obstructed Blades
Clogged blades are a fifth culprit for the symptom of “My mower starts and then dies immediately.” During long-term use, grass clippings, dirt and other contaminants can gather up around the mower blades as well as the mower deck. As a result, your mower’s engine can stutter under load, so the cutting performance is greatly reduced and even the mower stalls before getting to mow.
How to Fix:
- Turn off your mower and disconnect the spark plug wire in case of accidental start.
- Raise the mower deck to a higher level so you can access the underside of the mower.
- Inspect the mower blades for buildup, such as grass and dirt surrounding the blades.
- Use a brush or a scraper to remove the buildup while protecting your hands with gloves.
- Sharpen the blades with a sharpening stone or metal file if you notice they are nicked or dull.
- Reassemble the mower and reconnect the spark plug wire for small-area mower testing.
Blocked Fuel Line or Fuel Cap Vent
If the fuel line is clogged, it can interrupt the steady fuel flow. Consequently, the engine will run for a short while and then die as it runs out of fuel. Similarly, if the fuel cap vent is blocked, it can create a vacuum inside the fuel tank, which prevents the proper fuel flow to the engine and then your mower will stall a few minutes after you start it.
How to Fix:
- Locate the fuel line and fuel cap vent and check to see if there are visible dirt, debris por blockages.
- Check the fuel filter and replace it if it is worn out or extremely dirty.
- Clear the fuel line and vent hole with compressed air, small flexible brush and small pin or needle.
- Inspect the cap and fuel line for wear or cracks, and replace them if they are cracked.
- Reassemble the fuel line or fuel cap and then start your mower to test if it runs smoothly.
- Quick Checklist for Lawn Mower Starts Then Dies
- Drain old fuel and add fresh fuel
- Clean or rebuild the carburetor
- Clean or replace the air filter
- Inspect and replace the spark plug or wires when necessary
- Check the fuel lines, fuel cap and even fuel filters to see the blockages.
- Clean the buildup, dirt, and debris around the blades.
- Bring it to a pro when the problem persists
- Consider replacing your mower if all these steps fail
Wrapping up
At FridayParts, we’ve seen so many homeowners encountering issues like “lawn mower starts then dies” and helped them to address all these difficulties with our expertise as well as our vast lineups of lawn mower parts, including carburetors, blades, air filters, spark plugs and so on. Browse our category list to get back to uninterrupted mowing. Don’t let the quick stall ruin your mowing season.
