Briggs And Stratton Ignition Coil Testing (Troubleshoot Old Engines)

Let’s dive in and unlock the secrets to Briggs & Stratton ignition coil testing and troubleshooting old engines.

Introduction: Sparking Success – Why Ignition Coil Testing Matters

I’ve spent years tinkering with small engines, especially those workhorses from Briggs & Stratton. There’s a certain satisfaction in bringing a sputtering old engine back to life. But more often than not, the culprit behind a no-start situation is a faulty ignition coil. Think of the ignition coil as the heart of your engine’s electrical system. Without a healthy spark, your engine is just a collection of metal parts, destined to sit idle.

Testing and troubleshooting your Briggs & Stratton ignition coil isn’t just about fixing a problem; it’s about understanding the core principles of engine operation, saving money on repairs, and extending the life of your valuable equipment. Whether you’re a seasoned mechanic or a weekend warrior, mastering ignition coil testing will give you the confidence to tackle engine problems head-on.

Briggs & Stratton Ignition Coil Testing (Troubleshoot Old Engines)

Before diving into the specifics of ignition coil testing, it’s crucial to understand the purpose and function of an ignition coil in a Briggs & Stratton engine. The ignition coil is responsible for generating the high-voltage spark needed to ignite the air-fuel mixture in the cylinder, initiating the combustion process that powers the engine. Over time, ignition coils can fail due to factors such as heat, vibration, moisture, and general wear and tear.

1. Identifying the Need for Ignition Coil Testing

Before you even touch a multimeter, you need to determine if the ignition coil is the likely suspect. Here are some telltale signs:

Engine won’t start: This is the most common symptom. If the engine cranks but doesn’t fire, the ignition coil could be the problem.
Weak or intermittent spark: The engine might start and run poorly, or it might start sometimes but not others. This suggests a weakening coil.
Engine misfires: A misfire occurs when the air-fuel mixture doesn’t ignite properly. This can be caused by a weak spark.
Rough running engine: The engine might run unevenly, with noticeable vibrations or a lack of power.
Backfiring: This is a loud popping sound that occurs when unburned fuel ignites outside the cylinder. It can be a sign of timing issues, but a faulty coil can also contribute.

2. Safety First: Essential Precautions

Working with electrical components requires caution. Before you begin any testing, make sure to:

Disconnect the spark plug wire: This prevents accidental starting.
Remove the spark plug: This relieves compression and makes testing easier.
Use insulated tools: This protects you from electrical shock.
Work in a well-ventilated area: Fuel fumes can be dangerous.
Wear safety glasses: This protects your eyes from debris.

3. Visual Inspection: The First Step

Before you grab your tools, give the ignition coil a thorough visual inspection. Look for:

Cracks or breaks in the coil housing: These can indicate physical damage.
Corrosion on the terminals: Corrosion can impede electrical flow.
Burn marks: These suggest overheating, which can damage the coil.
Loose wiring: Make sure all connections are secure.

If you see any of these issues, the ignition coil is likely faulty and should be replaced.

4. Basic Spark Test: The Easiest Check

This is the simplest way to check if the coil is producing a spark.

Reconnect the spark plug wire to the spark plug.
Ground the spark plug: Hold the spark plug against a metal part of the engine while holding the insulated spark plug wire.
Pull the starter rope: Observe the spark plug gap.

Expected Result: You should see a strong, blue spark jumping across the spark plug gap. A weak, yellow spark or no spark at all indicates a problem with the ignition system, potentially the coil.

My Experience: I once spent hours troubleshooting an engine that wouldn’t start, only to discover that the spark plug wire was loose. A simple spark test would have saved me a lot of time!

5. Air Gap Adjustment: Critical for Spark Generation

The air gap is the distance between the ignition coil and the flywheel magnets. This gap is crucial for the coil to generate a sufficient spark.

Locate the ignition coil mounting bolts.
Loosen the mounting bolts.
Use a business card or a feeler gauge to set the gap: The recommended gap is typically between 0.010 and 0.014 inches (0.25 to 0.36 mm). Check your engine’s service manual for the exact specification.
Tighten the mounting bolts.

Why it’s Important: If the air gap is too wide, the coil won’t generate a strong enough spark. If it’s too narrow, the coil can overheat and fail.

How to Interpret: A properly set air gap ensures that the coil is operating within its designed parameters.

Relating to Other Metrics: A correctly set air gap can improve engine starting and overall performance, affecting fuel efficiency and power output.

6. Using a Multimeter: Advanced Coil Testing

A multimeter is an essential tool for diagnosing electrical problems. Here’s how to use it to test an ignition coil:

Resistance Test (Primary Winding):
- Set the multimeter to the ohms (Ω) setting.
- Disconnect the spark plug wire from the spark plug.
- Touch one probe to the coil’s primary terminal (where the low-voltage wire connects) and the other probe to the engine ground.
- Compare the reading to the manufacturer’s specifications.

Expected Result: The resistance should be within the specified range. A reading of zero ohms (short circuit) or infinite ohms (open circuit) indicates a faulty coil. Typical values are between 0.5 and 5 ohms, but always consult your engine’s service manual.

Resistance Test (Secondary Winding):
- Set the multimeter to the ohms (Ω) setting.
- Touch one probe to the spark plug terminal and the other probe to the engine ground.
- Compare the reading to the manufacturer’s specifications.

Expected Result: The resistance should be within the specified range. A reading of zero ohms (short circuit) or infinite ohms (open circuit) indicates a faulty coil. Typical values are between 3,000 and 15,000 ohms, but always consult your engine’s service manual.

Why it’s Important: Resistance tests help identify internal shorts, opens, or excessive resistance within the coil windings.

How to Interpret: Readings outside the specified range indicate a faulty coil that needs replacement.

Relating to Other Metrics: Resistance values directly correlate with spark strength and engine performance.

7. Condenser Testing (If Applicable):

Some older Briggs & Stratton engines utilize a condenser (also known as a capacitor) in the ignition system. The condenser helps to prevent arcing at the points and improves spark quality.

Visual Inspection: Look for any signs of physical damage, such as cracks or leaks.
Continuity Test: Use a multimeter to check for continuity between the condenser’s terminal and its case. There should be no continuity.
Capacitance Test: Use a multimeter with a capacitance testing function to measure the condenser’s capacitance. Compare the reading to the manufacturer’s specifications.

Why it’s Important: A faulty condenser can cause weak spark, misfires, and premature point wear.

How to Interpret: A condenser that shows continuity or has a capacitance value outside the specified range should be replaced.

Relating to Other Metrics: A properly functioning condenser contributes to a strong, consistent spark, improving engine starting and performance.

8. Low Tension Wire Test: Ensuring a Solid Connection

The low tension wire connects the ignition coil to the points (if equipped) or the electronic ignition module. A faulty wire can prevent the coil from firing.

Visual Inspection: Check the wire for any signs of damage, such as cracks, breaks, or corrosion.
Continuity Test: Use a multimeter to check for continuity between the two ends of the wire.

Why it’s Important: A broken or corroded wire can interrupt the flow of electricity to the coil, preventing it from firing.

How to Interpret: If the wire shows no continuity, it needs to be replaced.

Relating to Other Metrics: A solid low tension wire connection ensures that the coil receives the necessary signal to generate a spark.

9. Flywheel Key Inspection: Timing is Everything

The flywheel key is a small metal piece that aligns the flywheel with the crankshaft. If the key is sheared or damaged, the engine timing will be off, preventing it from starting.

Remove the Flywheel: This usually requires a flywheel puller.
Inspect the Key: Look for any signs of damage, such as shearing or bending.

Why it’s Important: A sheared flywheel key will throw off the engine timing, preventing the coil from firing at the correct time.

How to Interpret: If the flywheel key is damaged, it needs to be replaced.

Relating to Other Metrics: Proper engine timing is crucial for efficient combustion and optimal engine performance.

10. Points Inspection and Adjustment (If Applicable):

Older Briggs & Stratton engines used points and a condenser to control the ignition timing. If your engine has points, they need to be inspected and adjusted regularly.

Visual Inspection: Check the points for any signs of wear, burning, or pitting.
Point Gap Adjustment: Use a feeler gauge to set the point gap to the manufacturer’s specifications.

Why it’s Important: Worn or improperly adjusted points can cause weak spark, misfires, and poor engine performance.

How to Interpret: Points that are worn or pitted should be replaced. The point gap should be adjusted to the specified value.

Relating to Other Metrics: Properly adjusted points ensure that the coil fires at the correct time, optimizing combustion and engine performance.

11. Ignition Module Testing (If Applicable):

Many newer Briggs & Stratton engines use an electronic ignition module instead of points and a condenser. Testing an ignition module typically involves checking the air gap and the module’s output voltage.

Air Gap Adjustment: Ensure the air gap between the ignition module and the flywheel magnets is within the specified range.
Output Voltage Test: Use a peak voltage adapter and a multimeter to measure the module’s output voltage while cranking the engine. Compare the reading to the manufacturer’s specifications.

Why it’s Important: A faulty ignition module can prevent the coil from firing, resulting in a no-start condition.

How to Interpret: An ignition module that produces an output voltage outside the specified range should be replaced.

Relating to Other Metrics: A properly functioning ignition module provides the necessary signal to the coil, ensuring a strong, consistent spark.

12. Understanding the Relationship Between Metrics

It’s important to understand how these metrics are interconnected. For example:

Air Gap and Spark Strength: A properly set air gap is essential for generating a strong spark.
Coil Resistance and Spark Strength: Correct coil resistance values indicate a healthy coil capable of producing a strong spark.
Flywheel Key and Timing: A sheared flywheel key throws off the engine timing, preventing the coil from firing at the correct time.
Points/Ignition Module and Spark Timing: Properly functioning points or an ignition module ensure that the coil fires at the optimal time for combustion.

13. Case Studies: Real-World Examples

Let’s look at a couple of real-world examples of how I’ve used these techniques to troubleshoot ignition coil problems:

Case Study 1: The Stubborn Lawn Mower: A customer brought in a lawn mower that wouldn’t start. After performing a basic spark test, I found a weak, yellow spark. I then used a multimeter to test the coil resistance and found that the primary winding had a reading of zero ohms. This indicated a short circuit within the coil. Replacing the coil solved the problem.
Case Study 2: The Backfiring Generator: A generator was backfiring and running poorly. I suspected a timing issue. After removing the flywheel, I found that the flywheel key was partially sheared. Replacing the key restored the engine timing and eliminated the backfiring.

14. Troubleshooting Flowchart: A Systematic Approach

Here’s a simple flowchart to guide you through the troubleshooting process:

Engine won’t start or runs poorly?
Perform a visual inspection of the coil and wiring.
Is there any visible damage?
- Yes: Replace the coil or wiring.
- No: Proceed to step 4.
Perform a basic spark test.
Is there a strong, blue spark?
- Yes: The ignition system is likely not the problem. Investigate other potential causes.
- No: Proceed to step 6.
Adjust the air gap.
Repeat the spark test.
Is there a strong, blue spark?
- Yes: The air gap was the problem.
- No: Proceed to step 9.
Use a multimeter to test the coil resistance (primary and secondary windings).
Are the resistance values within the specified range?
- Yes: The coil is likely good. Investigate other potential causes, such as the flywheel key, points (if applicable), or ignition module (if applicable).
- No: Replace the coil.

15. Common Mistakes to Avoid

Not checking the air gap: This is a common oversight that can lead to misdiagnosis.
Not using a multimeter: A multimeter is essential for accurate coil testing.
Not consulting the service manual: The service manual provides valuable information, such as the correct air gap and coil resistance values.
Assuming the coil is bad without proper testing: Don’t replace the coil unless you’ve confirmed that it’s faulty.
Ignoring other potential causes: The ignition coil is not always the problem. Consider other potential causes, such as a faulty spark plug, a blocked fuel filter, or a compression issue.

16. Practical Examples

Example 1: Improving Fuel Efficiency: By ensuring a strong, consistent spark, you can optimize combustion and improve fuel efficiency. A weak spark can lead to incomplete combustion, wasting fuel and reducing power output.
Example 2: Extending Engine Life: By regularly inspecting and maintaining the ignition system, you can prevent premature engine wear and extend its lifespan. A faulty ignition coil can cause misfires, which can damage the engine’s internal components.
Example 3: Reducing Downtime: By quickly diagnosing and resolving ignition coil problems, you can minimize downtime and keep your equipment running smoothly. A faulty ignition coil can bring your work to a standstill.

17. Challenges Faced by Small-Scale Loggers and Firewood Suppliers

They may have limited access to tools, parts, and technical expertise. They may also be working with older equipment that is more prone to failure.

Here are some tips for small-scale loggers and firewood suppliers:

Invest in basic tools: A multimeter, a spark tester, and a feeler gauge are essential tools for diagnosing ignition system problems.
Learn basic troubleshooting techniques: This guide provides a good starting point.
Consult the service manual: The service manual contains valuable information about your engine.
Network with other loggers and suppliers: Share tips and advice with others in the industry.
Consider professional help: If you’re not comfortable working on your engine yourself, seek professional help.

18. Final Thoughts: Empowering Your Engine Know-How

Mastering Briggs & Stratton ignition coil testing is a valuable skill that can save you time, money, and frustration. By following the steps outlined in this guide, you can confidently diagnose and resolve ignition coil problems, keeping your engines running smoothly for years to come.

Remember, safety is always the top priority. Take your time, work carefully, and consult the service manual when in doubt. With a little practice, you’ll be able to troubleshoot ignition coil problems like a pro!

19. Guidance on Improving Future Projects

After completing a wood processing or firewood preparation project, I always take time to review the metrics I tracked and identify areas for improvement. Here’s how I apply these metrics to future projects:

Time Management: If I consistently underestimated the time required for certain tasks, I adjust my estimates for future projects. I also look for ways to streamline processes and eliminate bottlenecks.
Wood Volume Yield Efficiency: If I’m not getting the desired yield from my wood processing operations, I analyze my techniques and equipment to identify areas for improvement. This might involve adjusting saw settings, optimizing cutting patterns, or investing in new equipment.
Moisture Content Levels: If I’m struggling to achieve the desired moisture content in my firewood, I adjust my drying methods. This might involve improving ventilation, increasing drying time, or using a dehumidifier.
Equipment Downtime: If my equipment is experiencing frequent downtime, I investigate the root causes and take steps to prevent future breakdowns. This might involve performing regular maintenance, replacing worn parts, or upgrading to more reliable equipment.
Cost Analysis: I carefully track all project costs, including labor, materials, and equipment expenses. This allows me to identify areas where I can reduce costs and improve profitability.

20. Conclusion: Continuous Improvement is Key

By continuously tracking and analyzing these metrics, I can make data-driven decisions that improve the efficiency, cost-effectiveness, and quality of my wood processing and firewood preparation projects. Remember, continuous improvement is the key to success in any endeavor. Don’t be afraid to experiment, learn from your mistakes, and adapt your strategies as needed. With a little effort and attention to detail, you can achieve your goals and build a thriving business.