How to fix a stuck float on lawnmower, step by step


You are mowing your lawn when suddenly, your lawnmower chokes and sputters to a halt. The engine somehow does not get enough fuel. Another scenario arises when suddenly black smoke clouds start to come out of the exhaust. Both conditions occur due to a  problem with the carburetor of the lawnmower. Both of these scenarios may also lead to a misleading diagnosis that the gasket is blown. There is a fine line of discrimination between the two. But in many cases, the float in the carburetor is stuck, which is much easier to fix.

How to fix a stuck float on a lawnmower, step by step:

  • Step 1: Disable the gas supply
  • Step 2: Drain the gas from the carburetor
  • Step 3: Remove the carburetor bowl
  • Step 4: Pull the pivot pin from the float
  • Step 5: Inspect the needle valve
  • Step 6: Clean the internals and externals
  • Step 7: Replace the bowl gasket
  • Step 8: Reassemble and recheck
How to fix a stuck float on lawnmower, step by step 1

Stuck float on a lawnmower, temporary Repair:

  • Step 1: Free the float using impact
  • Step 2: Drain the fuel, and let it push the float
  • Step 3: Unclog using Carburetor cleaner
  • Step 4: Blow pressurized air into the carburetor

Before starting with the fix itself, it is good to know more about the parts involved. This makes the Repair and diagnosis easier.

Working of the lawnmower carburetor and the Float

What does a lawnmower carburetor do?

The carburetor is the part of a lawnmower that allows the fuel and air to mix before it goes to the cylinder. The working principle is venturi. When the air intake occurs, the flowing air velocity causes a pressure drop sucking the fuel to mix with it. The carburetor governs the fuel-air mix entering the engine with the help of the throttle. A tappet screw is present on the carburetor that controls the fuel amount.

● What is the purpose of the Float

A float is present inside a bowl that is filled with fresh gas from the tank. The float rises and enables a specific amount through the needle valve. If the float gets stuck, the fuel supply is practically halted, which causes the engine to stutter and eventually shut down.

● Confusion between a Lawnmower Blown Head Gasket and Stuck float

It is easy to mix a problem with the head gasket and a stuck float. But there, it is actually a very easy way to distinguish between them. With a blown head gasket, the engine puff and coughs if running, but with a stuck float, it produces smoke without puffing and shuts down instantly.

How to diagnose a stuck float

After understanding how the carburetor works, we can not check the symptoms from a stuck float. This will help to diagnose if there is a problem with the float:

  • The engine will not idle: Idling is the phenomenon that occurs when the lawnmower is at rest and no amount of throttle is applied. In the scenario where the float is stuck, it will not allow fuel to gather in the bowl, resulting in a halt of the engine instead of idling.  
  • Hesitation in operation: When you try to accelerate or push the throttle, the engine’s response is as if it is going to die out. But after a bit of lag, it catches up. If this lag is more than normal (hesitation), it indicates a problem with the float.
  • Sudden stop of the engine: If the float gets stuck, the engine will come to a sudden power drop and give black smoke. In most cases, a complete halt of the machine is observed.
  • Carburetor Overflow/ Flooding: If you inspect the carburetor, the fuel has flooded out of the top. There is a main column that acts as a blow valve and lets out fuel’s excessive pressure through the top. This indicates a malfunction from the float of the carburetor.
  • Engine misfiring: Another indicator or symptom of a sticking carburetor float is when the motor stalls or the engine fails. One or two cylinders do not get enough fuel or get too much fuel when the spark plugs give a spark. This occurs when the float is trapped, either in the open or in the closed position. The motor can stall, not idle smoothly, or fire back as the carburetor floats.

How to fix a stuck float on Lawnmower, Step-by-step:

Equipment required:

The tools and parts required for fixing a stuck float are:

  • Screwdriver
  • Wrench set
  • Pliers
  • Bowl Gasket
  • Float pin
  • Carburetor Cleaner
  • Collector Tank
  • Clips
  • Clean cloth/ rag

Temporary Fix:

If you do not have a lot of time and want a quick fix to solve the stuck float, you can use the following steps. This will work for a limited time and in no way should be seen a permanent fix.

•Step 1: Free the float using impact

  • Open the hood of the mower and locate the carburetor
  • Use a screwdriver and tap on top of the carburetor. Do not use a lot of force. A heavy blow can damage the carburetor.
  • Tap on the bowl part of the carburetor as well.
  • This can help get the carburetor’s float free itself as the clogging element’s dirt breaks away from tapping. If it works, do not expect it to last for long. If it does not help, continue with step 2.

•Step 2: Drain the fuel, and let it push the float

  • Close the fuel valve if your lawnmower has one
  • Open the drain plug present under the carburetor
  • Place a collector pan under the carburetor to collect the gas.
  • The flow of fuel with pressure from the bowl can remove the clogging element and free the bowl
  • Carefully reinstall the plug and clean the area for any gas spillage
  • If this fix works, do not expect it to last long. If it does not work, continue with step 3.

•Step 3: Unclog using Carburetor cleaner

  • Remove the intake pipe from the head of the carburetor.
  • Spray the carburetor cleaner into the manifold as well as the top portion of the carburetor
  • Let the dirt drain from the plug and let the carburetor settle for 20 – 30 minutes before restarting the engine.
  • If this fix works, you can expect it to last a little longer than the earlier steps’ fixes. If it does not work, continue with step 4.

•Step 4: Blow pressurized air into the carburetor

From the top of the carburetor, blow air and open the drain plug in the bowl. This will allow most of the dirt and clogging to be removed. Always try the use of the carburetor cleaner in step 3 first.

Permanent Repair:

To fix the problem of a sticking float more permanently, you can use the following steps:

•Step 1: Disable the gas supply

  • Remove the gas from the gas tank
  • Disconnect the fuel pipe coming from the fuel tank
  • Place a stopper or a clip to avoid any overflow from the remainder of the gas in the tank
  • Place a collector pan to prevent the spill of any remaining gas
  • Remove and clean the air filter as well

•Step 2: Drain the gas from the carburetor

  • Untighten the drain plug present in the carburetor bowl to let all the gas from the carburetor out.
  • Collect the fuel in a collector tank and clean the splashes, if any.

•Step 3: Remove the carburetor bowl

  • Unscrew the carburetor bowl and pull it off.

•Step 4: Pull the pivot pin of the float

  • Using a screwdriver push the pin from one side
  • Using a pair of tweezers or pliers, pull the pin out remove the float

•Step 5: Inspect the needle valve

  • Check for a clogged needle valve with the help from a flashlight

•Step 6: Clean the internals and externals

  • Spray the carburetor cleaner thoroughly on both the inside and outside. Using a cotton swab, clean away all the visible dirt

•Step 7: Replace the bowl gasket

  • Check if the gasket of the bowl is damaged. If so, replace the gasket.
  • Before reinstalling the gasket, remove the marking that the old gasket has formed.

•Step 8: Reassemble and recheck

  • Reassemble all the parts back. Always replace any part that seems damaged or has extreme wear and tear. For a complete rebuilding of the carburetor, you might take help from another guide on our blog.

Precautions:

  • Safety first: Use proper safety clothing, apron, gloves, insulation boots, and protective glasses
  • Save the fuel: Fuel from the line and carburetor must be collected in a bowl. This fuel can be reused to clean stuff, and the fuel contains dirt or sometimes water as well. It is not advisable to use it in the lawnmower again.
  • Minor details are taken care of: Perform all of the procedure under a good source of light. There are minute adjustments that are needed while assembling the carburetor.
  • Open-air procedure: These steps must be practiced in an open garden or park. Performing it in a closed shop or garage can be a bit dangerous. Closed air might have elevated temperatures, and fumes of gas might end up catching fire. 

Related Questions:

1. Can WD-40 be used as a carburetor cleaner?

Yes. You can use it as a carburetor cleaner. WD-40 is a synthetic chemical and an excellent solvent. It dissolves away dirt or corrosion present on any of the components of the carburetor.

2. What is carburetor fuel adjustment?

Making the best combination of air and fuel will help to improve the life of your engine. If your machine is running too rough, it’s necessary to change the mixture. Find the right idling speed to decrease engine tension. Try to prevent the engine from running too quickly or too slowly. Adjusting the carburetor idling screw in your lawnmower can be achieved with only a few basic measures and no special instruments.

Final Remarks:

One of the most critical components of a Lawnmower is the carburetor. It mixes the air and fuel and ensures that the engine runs fine. If you learn how to maintain your lawn mower carburetor, you can fix many of the common problems. This article explains how to solve a stuck float on a carburetor with both a quick fix and a more thorough method.

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