Colin FosterBy Colin Foster

Updated November 2026

A Craftsman riding lawn mower that won’t start after sitting is usually suffering from a dead or weak battery, stale fuel, a fouled spark plug, or a safety interlock that isn’t being satisfied. This guide walks you through the checks in the order that solves the problem fastest, so you can avoid replacing parts you don’t need.

Start With the Battery and Electrical Checks

Most no-start complaints after storage trace back to the battery. A lead-acid battery loses charge when it sits, and a deeply discharged one may still click or do nothing at all. Start here before touching the engine.

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  1. Set a multimeter to DC volts and measure across the battery terminals. A reading near 12.6 volts indicates a healthy, fully charged battery. Below about 12.2 volts, charge it before going further.
  2. Clean the terminals and cable clamps with a wire brush or baking soda and water. Corrosion blocks current even when the battery is good.
  3. Check that the battery is connected with the negative cable on the frame and the positive cable to the starter circuit, and that the fuse is intact.
  4. Charge the battery with a suitable maintainer for several hours, then try to start again.

If the engine cranks slowly or not at all after a full charge, the battery likely needs replacing. A starter solenoid or wiring fault is also possible, and a repair shop can test these if the basics don’t resolve it.

Deal With Old Fuel and the Carburetor

Gasoline that has sat for months can turn to varnish and gum up the carburetor jets. Ethanol-blended fuel is especially prone to this, because it absorbs moisture and separates over time. Check the fuel first: if it smells sour or looks dark, drain it.

Drain the tank and fuel line into an approved container, then refill with fresh gasoline. A fuel stabilizer added before storage prevents this problem in the next season. If the mower still won’t run, the carburetor may need cleaning. Many owners find that a carburetor cleaner spray, used with the bowl drained, clears clogged jets, though a rebuild kit may be needed for heavily gummed units.

Check the Spark Plug and Air Filter

A spark plug that has been sitting can develop carbon or oil fouling, and moisture can disrupt the spark. Remove the plug with a socket, inspect the tip, and clean or replace it. Set the gap to the value listed in your owner’s manual. Confirm the plug boot is firmly seated on the wire.

Check the air filter too. A clogged or damp filter restricts airflow and can make a cold engine hard to start. Replace a paper filter that is dirty, and clean a foam filter according to the manual.

Verify the Safety Switches

Craftsman riding mowers use safety interlocks that prevent starting unless certain conditions are met. Typical requirements include the operator being seated, the blade engagement switch being off, and the brake or transmission being in the correct position. If the seat switch is dirty, bent, or misaligned, the mower will act as if nobody is sitting on it.

  • Sit fully on the seat and try starting with the blade switch off.
  • Confirm the parking brake is engaged and the transmission is in neutral.
  • Inspect the seat switch and its wiring for damage, and clean the contacts.

Common mistakes

  • Repeatedly cranking the engine on a weak battery, which can damage the starter and drain what little charge remains.
  • Assuming the battery is fine because it looks normal. Test it with a meter.
  • Adding fresh gas on top of old fuel without draining the tank first.
  • Pulling the spark plug wire without checking the plug condition, then missing a fouled plug.
  • Ignoring the safety switches because the engine appears to be the problem.
  • A digital multimeter lets you measure battery voltage accurately, which helps you decide between charging and replacing. View on Amazon
  • A battery maintainer keeps the battery topped up during the off-season and prevents the discharge that causes most no-start problems. View on Amazon
  • Fuel stabilizer protects gasoline from breaking down during storage and keeps the carburetor clean. View on Amazon

FAQ

Can old gas really stop a riding mower from starting?

Yes. Gasoline that has aged can leave varnish in the carburetor jets and fuel passages, which blocks fuel flow. Draining the old fuel and refilling with fresh gas often restores normal starting.

Should I charge the battery or replace it?

Charge it first, then test the voltage. A battery that reads well after a full charge and cranks strongly can stay in service. If it won’t hold a charge or cranks weakly, replace it.

When should I take the mower to a repair shop?

If the basic checks don’t solve the problem, or you suspect a starter, solenoid, or wiring fault, a qualified small engine technician can test these parts. Consult a professional before working on fuel system components if you are unsure.

Conclusion

Work through the battery, fuel, spark plug and safety switches in that order, and most no-start problems after sitting are resolved without new parts. Storing the mower with fresh fuel stabilizer and a maintained battery will prevent the same problem next season. For related troubleshooting, see Craftsman Lawn Mower Won't Start After Sitting: 8 Fixes That Work and Riding Lawn Mower Won't Start After Winter: 7 Fixes to Try First.

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Colin Foster

About Colin Foster

Colin Foster is part of our editorial team and reviews and edits our lawn mowers guides, checking product details against manufacturer specifications and owner feedback.