Craftsman Lawn Mower Not Starting: Quick Fixes and Full Repair Guide – 2025

You pull the cord or turn the key—nothing. A Craftsman lawn mower not starting is frustrating, especially when the grass is already tall. The quickest fix? Start with fresh fuel, check the spark plug connection, and prime the engine. Many mowers spring back to life with these simple steps.

In this comprehensive guide, you’ll learn all the common reasons a Craftsman mower won’t start and how to fix each one—from fuel and spark issues to carburetor clogs, safety switch problems, and battery faults on electric start models. Follow along step by step, and by the end, you’ll have your mower running smoothly and know how to prevent starting problems for good.

Common Causes of a Craftsman Lawn Mower Not Starting

Stale or Contaminated Fuel

Gas older than 30–60 days can degrade and form varnish, clogging the carburetor and jets. Water or debris in the tank can also prevent ignition.

Flooded Engine

Over-priming or repeated starting attempts can flood the cylinder with fuel, wetting the spark plug and preventing ignition.

Bad Spark Plug or Loose Plug Wire

A fouled, wet, cracked, or improperly gapped spark plug will cause hard starts or no start. The spark plug boot can also loosen and lose contact.

Clogged Air Filter

A heavily soiled filter restricts airflow, creating a rich mixture that won’t ignite well.

Carburetor Blockage

Gummed jets, stuck float, or varnish buildup from old gas stops fuel from reaching the combustion chamber.

Safety Switch Engagement

Bail/kill switch, seat switch, blade engagement (PTO) switch, brake/clutch switch, or bagger switch on certain models can disable starting when not set correctly.

Fuel Line or Fuel Cap Vent Blockage

Cracked lines leak air or fuel; clogged lines or a non-venting cap creates a vacuum lock that stops fuel flow.

Battery/Starter Issues (Electric Start or Riding Mowers)

Weak battery, corroded terminals, blown fuse, bad starter solenoid, or faulty ignition switch prevent cranking.

Low Oil or Engine Damage

Some Craftsman engines have low-oil shutoff; low oil prevents ignition. Severe internal issues (rare) can also prevent start.

How to Fix a Craftsman Lawn Mower Not Starting

Method 1: Quick Start Checks (5–10 minutes)

Diagnosing the Issue

Use this method if the mower was running recently, or you store it properly and suspect a simple issue.

Fix Steps

1) Verify controls and safety switches:
– Ensure the blade control/bail bar is held tightly against the handle.
– Put the transmission in neutral (if applicable), and disengage the blade/PTO.
– On riding mowers: sit on the seat, set parking brake, shift to neutral.

2) Check fuel:
– Confirm there’s fresh gasoline (unleaded, 87+ octane, ethanol ≤10%). If older than 60 days, plan to replace.
– Shake mower gently; listen for slosh to confirm level.

3) Prime and start:
– Press the primer bulb 3–5 times if equipped (consult your model’s manual for exact count).
– Pull the cord firmly or turn the key. If the engine coughs but won’t start, go to Step 4.

4) Inspect the spark plug wire:
– Ensure the spark plug boot is fully seated with a firm click. Pull it off and push it back on to reseat.

5) Check the air filter:
– Open the air filter housing. If paper filter is dirty or wet, remove it; try starting briefly without it (no more than 30 seconds). If it starts, replace the filter.

Testing

• If the mower starts and runs, replace the filter if removed and keep using fresh fuel.
• If not, proceed to Method 2.

Method 2: Fuel Refresh and Flood Recovery (10–20 minutes)

Diagnosing the Issue

Use if the mower sat for a month or more, or it smells strongly of fuel after multiple failed starts.

Fix Steps

1) Replace stale fuel:
– Tip mower safely toward the side opposite the air filter and spark plug, or use a siphon to drain the tank into an approved container.
– Refill with fresh gasoline and add a fuel system cleaner/stabilizer (e.g., Sta-Bil, Sea Foam) per label.

2) Clear a flooded engine:
– Remove the spark plug boot and spark plug (use a 13/16″ or 5/8″ socket).
– Inspect the plug: if wet or sooty, dry it or replace it (NGK/Champion equivalents per engine model; common gap ~0.028–0.030″, check manual).
– With the plug removed, pull the starter cord 5–6 times to expel excess fuel.
– Reinstall and reconnect the plug.

3) Try starting with proper priming:
– Prime 1–2 times (or not at all if recently flooded) and start.

Testing

• Runs fine: you had stale fuel/flooding.
• Still won’t start: move to Method 3.

Method 3: Spark, Air, and Fuel Delivery Check (20–40 minutes)

Diagnosing the Issue

Use if quick fixes fail; this verifies fire, air, and fuel step-by-step.

Fix Steps

1) Check spark quality:
– Remove the spark plug, reconnect it to the boot, and ground the plug threads to the engine metal.
– Pull the cord and look for a strong blue spark. No spark or weak orange spark indicates a bad plug, coil, or kill switch issue.
– Replace the spark plug if in doubt. If still no spark, inspect the bail cable/kill switch and wiring for shorts.

2) Inspect and replace the air filter:
– Paper: replace if dirty or oil-soaked.
– Foam pre-filter: wash with warm soapy water, dry completely, lightly oil, squeeze out excess.

3) Verify fuel flow:
– With the fuel valve (if present) ON, remove the fuel line at the carb inlet and catch fuel in a container. You should see a steady stream.
– Weak/no flow: check for clogged line, filter, or a blocked fuel cap vent. Replace fuel line and filter if brittle/clogged.
– If flow is good, the carburetor may be clogged.

4) Test with carb cleaner:
– Spray a short burst of carb cleaner into the air intake. Try to start:
– Engine runs briefly and dies: carb needs cleaning (go to Method 4).
– No change: recheck spark and safety switches.

Testing

• If spark is strong and fuel/air are confirmed, move to carburetor service next.

Method 4: Clean the Carburetor and Jets (45–90 minutes)

Diagnosing the Issue

Old fuel varnish causes stuck floats, clogged main jets, and stuck needle valves—classic causes of no-start or starts-then-dies.

Fix Steps

1) Safety preparation:
– Warning: Disconnect the spark plug boot. Work in a ventilated area away from flames. Wear gloves and safety glasses.

2) Remove the carburetor:
– Shut off fuel valve or clamp the fuel line.
– Remove air filter housing and linkage rods carefully. Take photos for reassembly.
– Remove the carb bowl (usually 10 mm bolt). Watch for the bowl gasket and float.

3) Clean components:
– Inspect the bowl for varnish or debris; clean with carb cleaner.
– Remove the main jet and emulsion tube (accessible through the center bolt opening or behind a plastic welch plug depending on model).
– Spray carb cleaner through all passages until it exits other ports. Use compressed air to blow out passages (do not use wire on soft brass jets unless necessary).
– Ensure the float moves freely and the needle valve tip isn’t grooved. Replace if worn.

4) Reassemble with new gaskets:
– Install a new bowl gasket and carb-to-intake gasket if damaged. Reattach linkages and fuel line.

5) Prime and start:
– Turn fuel on, check for leaks, prime per instructions, and start.

Testing

• If it starts and runs, let it idle for 5 minutes and then mow lightly to clear any residue.
• If it only runs on choke or surges, the main jet may still be partially clogged; repeat cleaning or replace the carburetor.

Method 5: Safety Switches, Cables, and Ignition Kill Circuit (20–45 minutes)

Diagnosing the Issue

If the engine has spark intermittently or dies when you release the bail bar, suspect safety switches or a shorted kill wire.

Fix Steps

1) Bail cable and brake:
– Ensure the bail bar fully engages the engine brake and switch. Adjust the cable tension if the bar feels loose or doesn’t retract fully.

2) Kill wire inspection:
– Trace the thin kill wire from the coil to the switch. Look for pinches or rub-through causing a ground short. Temporarily disconnect at the coil to test for spark (Warning: engine may start; you must choke to stop).

3) Seat/Blade/Brake switches (riding mowers):
– Ensure PTO is off and brake engaged. Test continuity of switches with a multimeter; replace faulty switches.

Testing

• Consistent spark restored? Start normally. If not, the ignition coil may be faulty—replace with the correct part for your engine model.

Method 6: Battery, Starter, and Electrical (Electric Start and Riding Mowers) (20–60 minutes)

Diagnosing the Issue

If the engine doesn’t crank or cranks slowly, focus here.

Fix Steps

1) Battery:
– Measure voltage: ≥12.6V fully charged. Charge if 12.2–12.4V. Replace if it won’t hold 12.6V.
– Clean terminals; tighten cables.

2) Fuses and wiring:
– Check main fuse near solenoid/battery; replace if blown. Inspect ground strap to frame/engine.

3) Solenoid and starter:
– Listen for click when turning the key. Click but no crank: test solenoid. No click: ignition switch or safety circuit issue.
– Jump the solenoid large posts with an insulated tool briefly to test the starter (Warning: sparks possible). If starter spins, solenoid is faulty.

4) Ignition switch:
– Test continuity with a multimeter per pinout; replace if failing.

Testing

• Strong cranking with good spark and fuel should start. If it cranks well but still won’t fire, return to fuel/spark diagnostics.

How to Prevent Future Starting Issues

• Use fresh, ethanol-free fuel if possible (E0) or E10 with stabilizer. Add stabilizer with every fill if fuel may sit.
• Run the engine monthly for 5–10 minutes during the off-season.
• At end of season, drain the tank and carb bowl or run the mower dry.
• Replace or clean the air filter every 25 hours or each season.
• Replace the spark plug annually or every 100 hours.
• Keep the carburetor and fuel cap vent clean; replace brittle fuel lines.
• Store the mower in a dry, covered area to avoid moisture issues.

Pro Tips

• When diagnosing, change only one variable at a time to avoid confusion.
• Photograph linkage and hose routing before disassembly to ensure proper reassembly.
• If your engine only runs on half choke, the main jet is still restricted—clean or replace the jet.
• A quick field test: loosen the gas cap while trying to start; if it starts, the cap vent is blocked.
• Use a spark tester for a definitive spark check; it’s more reliable than just observing arc color.
• Don’t overtighten spark plugs; use 1/4 to 1/2 turn past finger tight for new plugs, or torque to manufacturer spec (often 18–22 ft-lb).
• For winter storage, fog the engine and change oil to prevent corrosion and make spring starts easier.

Professional Help

• When to call a pro:
• Repeated no-start after carb cleaning and fresh fuel
• Strong fuel smell mixed with oil or signs of internal damage (e.g., bent blade impact followed by no start)
• Electrical gremlins you can’t isolate, or repeated blown fuses

• Hydrostatic or transmission interlock issues on riders

• Choosing a service provider:

• Look for small engine techs certified for Briggs & Stratton, Kohler, or Honda (depending on your engine).

• Ask about turnaround time and warranty on repairs.

• Typical costs:

• Tune-up (plug, filter, blade sharpening): $80–$150
• Carburetor cleaning/rebuild: $90–$180
• Carburetor replacement: $60–$200 parts + labor

• Battery replacement (rider): $40–$120

• Warranty notes:

• Craftsman warranty often covers manufacturing defects, not stale fuel or wear parts. Keep receipts and maintenance records.

FAQ

Q: My Craftsman mower clicks but won’t start. What’s wrong?

A: A clicking sound typically points to a weak battery or a faulty solenoid. Check battery voltage (≥12.6V), clean terminals, and inspect the fuse. If the battery is good and you still hear clicks, test/replace the solenoid.

Q: It starts only with starter fluid. Why?

A: That means you have spark and compression, but poor fuel delivery. The carburetor or main jet is likely clogged. Clean or replace the carb and ensure good fuel flow from the tank.

Q: How do I know if the engine is flooded?

A: You’ll smell fuel, and the spark plug will be wet. Remove the plug, pull the starter a few times to clear the cylinder, dry or replace the plug, and try starting with minimal or no priming.

Q: What spark plug does my Craftsman mower use?

A: It depends on the engine brand/model (e.g., Briggs & Stratton, Honda, Kohler). Common types include Champion RJ19LM or NGK BPR6ES, but always check your engine’s manual or the old plug for the exact specification and gap.

Q: Why does my mower only run with the choke on?

A: That indicates a lean condition—usually a clogged main jet or air leak. Clean the carburetor thoroughly and replace gaskets. Inspect the intake boot and carb mounting gasket.

Q: Can bad gas really stop a mower from starting?

A: Yes. Gasoline starts degrading in 30–60 days, especially E10. It forms varnish that clogs jets and passages. Always use fresh fuel and consider a stabilizer.

Q: The pull cord is hard to pull. Is that normal?

A: No. A stuck blade due to debris, a bent crankshaft from an impact, or engine hydro-lock from oil/fuel can cause this. Disconnect the spark plug wire and check for blade obstructions first.

Alternative Solutions

If repeated carburetor cleanings fail or parts are scarce, replacement can be cost-effective.

Get Your Craftsman Lawn Mower Working Again

Following this guide, you now have multiple solutions to fix your Craftsman lawn mower not starting:
– Quick checks for fuel, spark, air, and safety switches
– Refreshing fuel and clearing a flooded engine
– Carburetor cleaning and replacement options
– Electrical diagnostics for battery, solenoid, and starter issues
– Preventive maintenance to avoid future no-starts

Don’t let a no-start ruin your weekend. Work through the methods in order—from quick fixes to deeper repairs—and you’ll have your Craftsman cutting clean again in no time.

Have you successfully fixed your Craftsman mower not starting? Share what worked for you in the comments to help other readers. Found this helpful? Bookmark this guide for quick reference before the next mow.