Lawn Mower Stalls When Tilted-Causes and Fixes

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Your lawn mower stalling when tilted can slow down your mowing operation, and that can be quite frustrating when you have a few acres to cover.

In this article, I share the common reasons your lawn mower stalls when tilted and simple fixes that you can carry out to solve these problems. 

Also, I explain the right ways to tilt your lawn mower, and corrective measures you can take when you tilt your mower the wrong way to prevent engine damage.

Reasons Why Your Lawn Mower Stalls When Tilted

The reasons your lawn mower stalls when tilted include:

  • Blocked/saturated fuel cap vent
  • Oil leakage into the air filter
  • Blocked fuel float
  • Damaged carburetor
  • Faulty spark plug

Lawn Mower Stalls When Tilted: Causes And Fixes

1.  Blocked/Soaked Fuel Cap Vent


Fuel can leak into the carbon in the fuel cap vent when you tilt your lawn mower. This restricts air from getting into the fuel system through the fuel cap air vent.

The fuel cap of your lawn mower has a little air vent lid that allows air to enter the tank to avoid a vacuum from building up as the fuel level reduces. 

A vapor lock occurs when the fuel cap vent is soaked with fuel or blocked, preventing air from entering the fuel tank. This reduces the flow of fuel to the mower’s engine and can cause the lawn mower to stall when tilted.


  • Clean the fuel cap and allow the vent to dry.
  • If the problem persists, the fuel cap vent might be blocked or damaged and should be replaced.

2. Oil Leakage Into The Air Filter

Oil from the engine can find its way into the carburetor when the lawn mower is tilted. The air filter of the carburetor is designed to capture dirt, dirt particles, debris, and other impurities, excluding oil.

The engine oil clogs the air filter once it comes in contact with it. As a result, contaminants and impurities flow freely into the engine, affecting overall engine performance. This can cause the engine to stall when tilted.

Reasons Why Oil Might Leak Into The Air Filter

Oil can leak into the air filter as a result of one of the following:

  • A clogged Positive Crankcase Ventilation (PCV) valve

A PCV valve is similar to an engine oil filter. It becomes clogged with too much debris (from the engine oil) and needs to be replaced once this happens.

Excessive oil will blow through the PCV valve and into the air filter system if the PCV valve is clogged.

  • Worn-out piston rings

When piston rings deteriorate, they become looser and this can lead to an increase in crankcase pressure, which, as previously mentioned, causes more oil to flow through the PCV valve and into the air intake.

  • Clogged oil passages

The last potential cause of engine oil clogging into the air filter is blocked oil passageways. When the engine oil and filter have not been changed after about 50 hours of active use, this symptom typically appears. 

It results from the buildup of engine dirt or excessive carbon residues inside the crankcase. Inefficient oil flow results in high engine oil pressure, which pushes additional oil through the PCV valve and into the air filter.


  • You will notice that the air filter is soaked with oil if this is the case.
  • Replace the old air filter with a new one to allow optimum engine performance.
  • A small engine technician should be contacted to troubleshoot and identify the cause of the problem if the new air filter gets clogged.

3. Blocked Fuel Float

Fuel can leak into the engine of your lawn mower when it is tilted if the fuel float becomes stuck.

The fuel float can become stuck, allowing fuel to leak from the carburetor into the vent tube, air filter, and other parts of your lawn mower engine. 

The fuel float is intended to maintain pressure inside the carburetor by shutting off the system at a set fuel level.

Tilting your lawn mower can cause an overflow of fuel into the engine system. The fuel vent is not able to control the fuel level when it becomes stuck/blocked with impurities and this can cause your lawn mower to stall when tilted.


The blocked fuel float should be replaced with a new one.

4. Damaged Carburetor


A damaged carburetor can also cause fuel to leak into the air filter when you tilt your lawn mower.

When the carburetor is broken or damaged, fuel escapes through the cracks into the air filter and clogs it, causing the engine to flood and eventually stall when tilted.


  • An experienced technician should fix the carburetor
  • The carburetor should be replaced if the damage is severe.

5. Faulty Spark Plug


The lawn mower’s spark plug might be contaminated with fuel or oil if it stalls when tilted. This could be a result of escaped oil or fuel from the fuel vent.


  • Remove the spark plug and examine for visible signs of fuel or oil stain
  • Clean and allow to dry if it is contaminated
  • Replace the spark plug if the problem persists

Can A Bad Battery Cause A Lawn Mower To Stall?

Yes, a bad battery can cause a lawn mower to stall. The battery of your lawn mower generates charges that help to keep the lawn mower’s engine running.

The amount of charge produced by a bad battery is reduced, affecting the engine motion and the overall performance of the lawn mower. This shortage in battery charge production can eventually cause your lawn mower to stall.

How To Diagnose A Bad Battery

You will need a Digital Multimeter for the diagnosis.

Step 1: Take off the lawn mower’s seat to provide access to the battery.

Step 2: Remove the lawn mower’s battery.

Step 3: Connect the digital multimeter to the battery, connecting the red pin of the multimeter to the positive terminal and the black pin to the negative terminal. Read the number of volts displayed by the multimeter.

The number of volts read by the multimeter should be about 12-12.5 volts. Anything below this is low and can cause your mower to stall. 

The battery of the lawn mower should be recharged/replaced if the volt of the battery falls below this number.

The Right Way To Tilt Your Lawn Mower

You might tilt your lawn mower to inspect the engine, change the blades, or service the engine. It is important that you understand the right way to tilt your lawn mower.

Tilting your lawn mower incorrectly can result in the following problems:

  • Fuel leakage
  • Saturated air filter
  • Blocked fuel vent
  • Fuel-oil mixture
  • Severe engine problems

The right way to tilt your lawn mower’s engine includes:

1.  Air Filter/Carburetor Side Up

Identify the air filter/carburetor side of your lawn mower before tilting it. This is the side that should face the sky when you tilt your lawn mower.

This helps to avoid problems of fuel leakage into the fuel vent, leaking oil, soaked air filter, etc.

How To Identify The Carburetor/Air Filter Side Of Your Lawn Mower

How do you identify the carburetor/ air filter side of your lawn mower before tilting it? 

The carburetor may not be very visible on some lawn mowers, but fortunately, the air filter cover shares the same space as the carburetor and is more visible and easy to spot.

An air filter and its cover can be recognized by the following features:

  • positioned on the engine’s side above the carburetor
  • easily reachable
  • created from plastic (black usually)
  • readily removable
  • often rectangle-shaped

2. Straight Back Resting On Its Wheels

Pull the front end of your lawn mower upwards allowing it to naturally rest on its wheels.

This is the best way to tilt your lawn mower in terms of minimizing oil and fuel leakage. The disadvantage of this method is that you would have to get on your back to get complete access when servicing your lawn mower’s engine.

What To Do If You Tilt Your Lawn Mower The Wrong Way

Here are some corrective measures to take if you tilt your lawn mower the wrong way before trying to start it:

  • Get it upright on its wheels and clean any visible spilled fuel or oil.
  • Check the air filter. Replace the air filter with a new one if it is saturated with fuel or oil to prevent engine damage.
  • Check the spark plug for oil or fuel contamination. This is known as spark plug fouling and is caused by fuel flooding and oil leakage.
  • Change the spark plug if it is contaminated.
  • Check your oil level and top up if necessary.
  • Allow the engine to sit for about 2-5 minutes and start it.


Some of the reasons your lawn mower stalls when tilted include a blocked fuel cap vent, damaged carburetor, contaminated spark plug, etc. 

To determine the root cause and solve the problem, carefully examine and troubleshoot the vital parts of your lawn mower’s engine using the tips recommended in this article. Then, apply the recommended fixes.