Lawn Mower Won’t Stay Running: Causes and Fixes (Model-Wise)

When your lawn mower starts and then suddenly stops, it’s one of the most frustrating problems to face — especially when you just fueled up and pulled the cord. Whether your mower dies after 2 seconds, runs only with choke, or needs starting fluid to stay running, the problem usually traces back to fuel, air, or spark issues.

This guide covers:
✅ Why a lawn mower won’t keep running
✅ Fixes for every cause
✅ Model-wise troubleshooting (Craftsman, Honda, Toro, John Deere, etc.)
✅ Common problems with both gas and electric mowers

🌿 Why Lawn Mowers Don’t Stay Running

If your mower starts but won’t stay on, the issue falls under one of three main systems:

1. Fuel system – Clogged carburetor, dirty fuel, or blocked fuel line
2. Air system – Dirty air filter or carburetor jet
3. Ignition system – Weak spark plug or coil issues

Other possibilities include bad fuel caps, faulty chokes, and vacuum leaks.

⚙️ Common Symptoms & Their Meanings

🧩 Step-by-Step Troubleshooting Guide

Let’s go through the main systems and their fixes one by one.

🔹 1. Check the Fuel System

Dirty, stale, or ethanol-contaminated gas is the #1 reason mowers won’t stay running.

Common Causes:

• Fuel older than 30 days
• Clogged carburetor jets
• Blocked fuel filter or fuel line
• Vent hole in fuel cap clogged (causing vapor lock)

✅ Fix:

1. Drain old fuel completely.
2. Add fresh unleaded gasoline (87 octane) or non-ethanol fuel.
3. Clean the carburetor bowl and jets with carb cleaner.
4. Replace the fuel filter.
5. Clean the fuel tank cap vent.

💡 Tip: If the mower only runs on choke, your carburetor is dirty or your main jet is partially blocked.

🔹 2. Clean or Replace the Air Filter

A clogged air filter restricts oxygen, causing the mower to choke or stall.

✅ Fix:

1. Remove the air filter cover.
2. Tap or blow out debris.
3. Wash foam filters in soap and water; replace if deteriorated.
4. Replace paper filters if dirty.

🧠 Rule of thumb: Replace air filters every 25 hours of mowing.

🔹 3. Inspect the Spark Plug

A fouled spark plug can cause intermittent firing — your engine starts but dies quickly.

✅ Fix:

1. Remove and inspect spark plug.
2. Clean carbon buildup with a wire brush.
3. Check gap (typically 0.030–0.035 in).
4. Replace plug if it’s corroded or blackened.

🔹 4. Check Carburetor Function

If your mower runs for 2 seconds and dies, fuel isn’t properly flowing from carburetor to engine.

✅ Fix:

1. Remove carburetor bowl.
2. Clean with carb cleaner spray and a fine wire.
3. Ensure float moves freely and needle isn’t stuck.
4. Reassemble and install a new gasket if needed.

🔧 For stubborn clogs, use a carburetor rebuild kit (inexpensive and effective).

🔹 5. Inspect the Fuel Cap

A blocked fuel cap vent causes a vacuum in the tank, preventing fuel from flowing.

✅ Fix:

1. Loosen the fuel cap slightly and start the mower.
2. If it runs normally, clean or replace the cap.

🔹 6. Check Ignition Coil & Kill Switch

If the mower starts and dies after warming up, it could be an ignition coil issue.

✅ Fix:

1. Test for spark using a spark tester.
2. If spark stops after heating, replace the coil.
3. Ensure the kill switch wire isn’t shorting against the frame.

🔹 7. Inspect the Choke System

If your mower runs only with choke on, it means your mixture is too lean (not enough fuel).

✅ Fix:

• Clean carb jets
• Adjust choke linkage
• Replace gaskets that may be allowing air leaks

🔹 8. For New Lawn Mowers That Won’t Stay Running

Brand-new mowers sometimes have leftover shipping oil or debris.

✅ Fix:

• Drain the factory test fuel residue.
• Clean or replace the spark plug.
• Run for 15 minutes after fueling with fresh gasoline.
• Check that the fuel shutoff valve (if present) is open.

🧠 Special Cases

🧯 Lawn Mower Won’t Stay Running Without Starting Fluid

Your carburetor isn’t pulling fuel.
✅ Fix: Clean the main jet and replace the fuel filter.

🔥 Lawn Mower Won’t Stay Running Without Choke

The carburetor is too lean — likely from a vacuum leak or partially clogged jet.
✅ Fix: Tighten carburetor bolts, replace intake gasket, and clean jets.

⚡ Lawn Mower Runs for 2 Seconds Then Dies

Classic symptom of a dirty main jet or blocked fuel cap vent.
✅ Fix: Clean carburetor and vent hole in fuel cap.

🧩 Model-Wise Causes and Fixes

Each brand has its own quirks — here’s what to look for:

🟥 Craftsman Lawn Mower

Common Causes:

• Dirty carburetor or air filter
• Bad fuel or faulty fuel solenoid

Fixes:

• Clean carb and replace air filter
• Replace fuel solenoid under carburetor bowl if engine dies after a few seconds

🟩 Husqvarna Lawn Mower

Common Causes:

• Clogged fuel filter or carb jet
• Weak ignition coil

Fixes:

• Replace inline fuel filter
• Clean carb and check spark plug and coil

🟦 Toro Lawn Mower

Common Causes:

• Debris in carburetor
• Fuel line vacuum blockage

Fixes:

• Remove float bowl, clean jet holes
• Replace cracked fuel lines and gas cap

🟨 John Deere Lawn Mower

Common Causes:

• Old gas or water in tank
• Blocked fuel filter or breather

Fixes:

• Drain and refill with fresh gas
• Replace fuel filter, check breather hoses

🟧 Cub Cadet Lawn Mower

Common Causes:

• Gummed carburetor after winter storage
• Sticking choke linkage

Fixes:

• Clean carb, lubricate choke linkage
• Use stabilizer in fuel during storage

🔵 Bad Boy Lawn Mower

Common Causes:

• Clogged carb jets or fuel solenoid malfunction

Fixes:

• Clean jets, replace solenoid under carb bowl

🟣 Exmark Lawn Mower

Common Causes:

• Dirty fuel injectors or carb (on older models)
• Bad ignition switch

Fixes:

• Clean injectors/carb
• Check for consistent voltage to the coil

🟫 Ariens Lawn Mower

Common Causes:

• Fuel cap vacuum issue
• Water in gas

Fixes:

• Replace fuel cap, drain and refill tank

🟠 STIHL Lawn Mower

Common Causes:

• Clogged air filter or carburetor
• Battery (in RMA models) not seated

Fixes:

• Clean or replace air filter
• Reinstall battery or clean contacts

🟢 Greenworks Lawn Mower

(Electric models)

Common Causes:

• Battery overheating or not fully seated
• Faulty start switch

Fixes:

• Let battery cool 10–15 minutes
• Reseat battery or replace switch

⚫ Robert Bosch GmbH (Bosch) Lawn Mowers

Common Causes:

• Overheated motor protection mode
• Faulty battery connection

Fixes:

• Wait for cooldown, clean terminals, recharge battery

🔵 Scag Lawn Mower

Common Causes:

• Dirty carburetor or air leak in intake
• Stuck choke cable

Fixes:

• Replace air filter, inspect gaskets, clean carb

🔴 Snapper Lawn Mower

Common Causes:

• Blocked fuel line or dirty carb bowl

Fixes:

• Clean lines, drain bowl, add fresh gas

⚙️ ATCO Lawn Mower

Common Causes:

• Dirty spark plug or moisture in carb

Fixes:

• Replace spark plug, dry carb and bowl

🔩 Briggs & Stratton Engine (Most Common Across Brands)

Common Causes:

• Clogged carburetor jet
• Old fuel residue

Fixes:

• Clean carb with B&S-approved cleaner
• Replace diaphragm and gaskets

⚡ EGO Lawn Mower

(Electric lithium models)

Common Causes:

• Overloaded motor or low battery voltage

Fixes:

• Recharge fully
• Clean blade area — debris can cause shutdown

🟠 Gravely Lawn Mower

Common Causes:

• Clogged fuel filter or dirty air filter

Fixes:

• Replace filters, check for vacuum leaks

🔵 Hart Lawn Mower

Common Causes:

• Low battery or blade jam (electric)

Fixes:

• Recharge or reset battery, clean deck

🔴 Honda Lawn Mower

Common Causes:

• Blocked carb jets (especially on GCV engines)

Fixes:

• Remove carb bowl, clean jets
• Replace gaskets

🟢 Hustler Lawn Mower

Common Causes:

• Fuel delivery issues or electrical ground fault

Fixes:

• Clean carb, tighten ground wires on ignition system

🟣 MTD Holdings Lawn Mower

(Covers Troy-Bilt, Yard Machines, etc.)

Common Causes:

• Blocked fuel line, old gas

Fixes:

• Drain tank, replace fuel line and filter

🟩 STIGA Lawn Mower

Common Causes:

• Carburetor clogged or governor stuck

Fixes:

• Clean carburetor, lubricate governor linkage

🧰 Quick Reference: Lawn Mower Starts Then Dies (Causes & Fixes)

🧠 Pro Maintenance Tips

1. Use fresh, ethanol-free fuel (or add a stabilizer if storing).
2. Clean air filters every 25 hours.
3. Run the mower dry before winter to prevent carb gumming.
4. Keep spark plugs clean and replace yearly.
5. Inspect fuel caps for venting issues regularly.

🪫 For Electric & Battery Mowers

If your Greenworks, EGO, or Bosch mower keeps shutting off:

• Clean grass buildup near blade motor.
• Ensure battery is fully charged and cooled.
• Check safety handle or start button — many models shut off if not held firmly.

✅ Summary: Key Fixes at a Glance

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David Holtzman

I’m David man behind Lawn Mowerly; I’ve been dealing with lawnmowers and Tractors with my father since I was a kid. I know every make and model and what each one is capable of and love helping people find the perfect equipment for their needs.