If you’ve ever struggled with a mower that just won’t start, chances are the ignition coil could be the culprit. The ignition coil in a Briggs & Stratton engine is responsible for generating the spark that ignites the air-fuel mixture in the engine, so if the coil is faulty, your engine won’t start or run properly. I’ve been through this frustrating process, and luckily, diagnosing and fixing a coil problem is pretty straightforward.
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Here’s a step-by-step guide to help you troubleshoot and solve ignition coil problems on a Briggs & Stratton engine.
Tools and Materials You’ll Need:
- Multimeter (for testing the coil)
- Socket wrench (to remove the engine cover)
- Screwdriver
- Spark plug tester (optional)
- New ignition coil (if replacement is needed)
- Feeler gauge (for coil gap adjustment)
- Work gloves (for safety)
Step-by-Step Guide to Solving Briggs & Stratton Coil Problems
1. Check for Symptoms of a Bad Ignition Coil
Before diagnosing, look for common signs of a bad ignition coil in your Briggs & Stratton engine:
- Engine won’t start: This is the most obvious symptom. If the engine turns over but won’t start, it’s often due to a lack of spark.
- Intermittent stalling: If the engine starts but stalls after running for a few minutes, the coil may be overheating and failing.
- No spark: If you’ve tested the spark plug and there’s no spark, the ignition coil could be faulty.
2. Check the Spark Plug
Before assuming the ignition coil is faulty, it’s essential to check the spark plug, since a bad plug could cause similar symptoms. Here’s how:
- Remove the spark plug using a socket wrench.
- Inspect the plug for signs of wear, fouling, or damage. If it’s dirty, clean it with a wire brush or replace it if needed.
- Use a spark plug tester to check for a spark. If there’s no spark, move on to checking the ignition coil.
3. Access the Ignition Coil
To test or replace the ignition coil, you need to access it by removing the engine cover:
- Disconnect the spark plug wire for safety.
- Remove the engine cover by unscrewing the bolts with a socket wrench. The cover is usually held in place by a few bolts.
- Locate the ignition coil, which is mounted near the flywheel and connected to the spark plug wire.
4. Test the Ignition Coil with a Multimeter
To confirm that the ignition coil is the problem, you’ll need to test it using a multimeter. Here’s how:
- Set the multimeter to the ohms (Ω) setting.
- Disconnect the small kill wire connected to the coil.
- Place one probe on the metal armature (ground) of the ignition coil.
- Place the other probe on the spark plug wire terminal of the coil.
You’re looking for a resistance reading between 2,500 and 5,000 ohms. If your multimeter shows an open circuit (infinite resistance) or a reading outside this range, it’s a sign the coil is faulty and needs to be replaced.
5. Replace the Ignition Coil (If Necessary)
If your coil test indicates a fault, replacing the ignition coil is the best solution. Here’s how:
- Remove the old coil: Unscrew the mounting bolts holding the coil in place and disconnect the spark plug wire.
- Install the new coil: Position the new coil over the flywheel, ensuring it is aligned correctly.
- Set the coil gap: Use a feeler gauge to set the gap between the ignition coil and the flywheel. The correct gap for most Briggs & Stratton engines is 0.010 – 0.015 inches. Insert the feeler gauge between the coil and the flywheel magnets, then tighten the coil bolts to secure it in place.
6. Reassemble and Test the Engine
- Reconnect the spark plug wire to the new coil.
- Reinstall the engine cover and tighten the bolts.
- Reconnect the spark plug and try starting the engine.
If the engine starts smoothly, your coil replacement was successful. If the problem persists, double-check the coil gap and ensure the spark plug is in good condition.
Troubleshooting Tips
- Engine runs but misfires: If the engine is running but misfiring or stalling intermittently, check the ignition coil again. Sometimes the coil works when cold but fails when it heats up.
- No spark but new coil installed: Double-check that the kill wire isn’t damaged or grounding somewhere, which can cut off the spark.
- Flywheel key: If the engine still won’t start after coil replacement, inspect the flywheel key. A sheared key can prevent the engine from starting even with a functioning coil.
Final Thoughts
Fixing ignition coil problems on a Briggs & Stratton engine doesn’t have to be difficult. With basic tools and a multimeter, you can quickly diagnose the issue and replace the coil if necessary. Remember to check the spark plug and wiring before assuming the coil is the problem, and always ensure the coil gap is set correctly for smooth engine performance. Following these steps will have your engine running smoothly in no time!