how to test a craftsman lawn mower with no spark

Daniel Parker

3 min read

·

19-01-2025

1

0

Share

A Craftsman lawn mower refusing to start can be frustrating. One common culprit is a lack of spark. This comprehensive guide will walk you through systematically testing your Craftsman mower to pinpoint the cause of the no-spark issue and get you back to mowing. We'll cover everything from simple checks to more advanced troubleshooting.

I. Safety First!

Before you begin any troubleshooting, prioritize safety:

• Disconnect the spark plug wire: This prevents accidental shocks.
• Ensure the mower is off and cooled down: Never work on a hot engine.
• Wear appropriate safety glasses and gloves: Protect yourself from potential hazards.

II. Initial Checks: The Easy Wins

Before diving into complex tests, let's address the simple things that often cause no-spark issues:

A. Fuel and Air

1. Check the fuel: Is the gas tank full enough? Is the fuel fresh (old gas can cause problems)? A clogged fuel filter can also be the cause of a no-start condition. Replace if necessary.
2. Inspect the air filter: A dirty air filter restricts airflow to the engine, potentially causing starting issues. Clean or replace it if needed. Refer to your owner's manual for instructions.

B. Battery and Connections

1. Check the battery: Is it adequately charged? Use a multimeter to test the voltage. A weak battery can prevent the ignition system from functioning correctly. A fully charged 12V battery should read around 12.6V.
2. Inspect the battery terminals and connections: Look for corrosion or loose connections. Clean the terminals with a wire brush and tighten connections.

C. Spark Plug

1. Inspect the spark plug: Remove the spark plug and visually inspect it. Look for cracks, fouling (carbon buildup), or excessive wear. Replace it if necessary. A gapped spark plug is critical. Use a feeler gauge to ensure it's correctly gapped according to the manufacturer's specifications found in your owner's manual.

III. Testing for Spark: The Crucial Step

If the basic checks don't reveal the problem, it's time to test for spark:

A. Testing the Spark Plug

1. Reconnect the spark plug wire to the spark plug.
2. Ground the spark plug: Hold the spark plug metal threads against the engine block (a metal part of the engine). Ensure good contact.
3. Have a helper crank the engine: While your helper cranks the engine, observe the spark plug gap. You should see a bright blue spark jumping across the gap. If no spark appears, move onto the next step.

B. Testing the Ignition Coil

A faulty ignition coil is a common cause of a no-spark condition. You’ll need a multimeter for this step.

1. Locate the ignition coil: Usually found near the spark plug. Consult your owner's manual for the exact location.
2. Check coil resistance: Use a multimeter set to the ohms setting to measure the resistance across the coil's primary and secondary windings. Your owner's manual should give you the correct resistance values to look for; they vary across models. Resistance outside this range indicates a faulty coil.

C. Testing the Ignition Switch and Wiring

Problems within the wiring harness or ignition switch can also interrupt spark delivery.

1. Inspect the wiring: Look for any visible damage or loose connections in the wiring harness between the ignition switch, coil, and spark plug. Repair or replace any damaged wires.
2. Check the ignition switch: This is more advanced and might require testing with a multimeter to ensure power is reaching the coil when the switch is activated. This may require the assistance of a qualified mechanic.

IV. If No Spark is Still Found

If you've tested everything above and still have no spark, the problem is likely more complex and may require professional help. This could involve:

• Faulty magneto: Some Craftsman mowers use a magneto system for ignition, and testing this is best left to a professional.
• Stator issues: Similar to the magneto, a problem with the stator will prevent spark.
• Electronic control module (ECM) problems: Some modern mowers use an ECM, and a faulty ECM requires specialized tools and knowledge for diagnosis and repair.

V. Preventive Maintenance

Regular maintenance can help prevent no-spark issues:

• Change the spark plug annually: This is a simple and inexpensive way to prevent problems.
• Clean or replace the air filter regularly: Refer to your owner's manual for recommended intervals.
• Keep the mower's battery charged: Store it properly during off-season.

By following these steps, you can effectively troubleshoot your Craftsman lawn mower's no-spark problem. If you're uncomfortable performing these tests, it's always best to seek assistance from a qualified repair technician. Remember safety first!