If you're someone who owns a small engine-powered lawn mower, chainsaw, or leaf blower, you know how frustrating it can be when your equipment won't start. One of the most common culprits of small engine failure is a faulty ignition coil.
Testing ignition coil resistance (ohms) is a simple process that can help you diagnose any issues and get your equipment up and running again. Required tools are a multimeter and this ignition coil resistance chart.
A small engine ignition coil resistance chart provides information about the acceptable range of resistance values for the ignition coil in a small engine.
You'll find comprehensive testing instructions below this helpful coil ohm testing guide.
Table of Contents
Ignition Coil Resistance Chart - Instructions
Current flow through point B of the coil on the resistance chart is directional. If your negative lead is attached to point B of your coil, as seen on this chart, your multimeter should give an infinite reading to both points A and C.
If your positive multimeter lead is touching point B, as pictured on this chart, you will get a reading to points A and C.
Make sure you connect the right lead to each section, as shown by the + and - in the top left corner of this ignition coil resistance chart.
Note that while a low resistance reading may seem like a good thing, it can actually be a sign of a problem.
Insufficient resistance can damage other components in your small engine, so it's important to always check the compatibility of your coil with your specific type of equipment.
The ignition coil is a crucial component of the ignition system that generates the high voltage needed to ignite the fuel in the combustion chamber. However, like any other electrical component, ignition coils can fail over time due to wear and tear, overheating, or other factors.
By regularly testing your ignition coil's resistance, you can catch issues early and prevent costly repairs down the line.
How to Test a Small Engine Ignition Coil
To keep your small engine or 2-stroke engine running smoothly, regularly check the ignition coil.
The ignition coil is responsible for creating the spark that ignites the fuel in your engine. A faulty ignition coil can lead to engine misfires, hard starting, and poor performance.
Testing your ignition coil can help you diagnose any issues and keep your engine running smoothly.
First, remove the spark plug wire from the spark plug.
Next, set the Ohm resistance on your multimeter to the desired range and then attach the multimeter's positive lead to the ignition coil's positive terminal and the negative lead to the negative terminal.
Check the resistance reading on the multimeter and compare it to the manufacturer's specifications, or the resistance chart above. If the reading is outside of the specified range, it's most likely time to replace the ignition coil.
Regularly testing your ignition coil can help you avoid costly repairs and keep your engine running smoothly.
Basic Coil Resistance Troubleshooting Steps
If you suspect that there's an issue with your 2-stroke ignition coil, you can perform some basic tests to identify the problem. Here are the steps to follow:
Step 1: Disconnect the Spark Plug Wire
Before you start testing the ignition coil, make sure you disconnect the spark plug wire from the spark plug to prevent any accidental firing.
Step 2: Remove the Ignition Coil
Remove the ignition coil from the engine. You may need to consult the owner's manual to find out where it's located and how to remove it.
Step 3: Test the Primary Coil
Using a multimeter, test the primary coil by measuring the resistance between the two primary terminals. The reading should be around 0.4 to 2 ohms.
If the reading is outside of this range, the primary coil is faulty and needs to be replaced.
Step 4: Test the Secondary Coil
Next, test the secondary coil by measuring the resistance between the primary terminal and the spark plug terminal. The reading should be around 6,000 to 10,000 ohms.
If the reading is outside of this range, the secondary coil is faulty and needs to be replaced.
Step 5: Test the Resistance
Finally, test the resistance between the spark plug terminal and the ground. The reading should be infinite.
If it's not, there's a short circuit and the ignition coil needs to be replaced.
Bad Ignition Coil Symptoms
One of the most common symptoms of a bad coil is misfiring. If your engine is misfiring, it means that one or more cylinders are not firing correctly. This can cause a range of problems, including reduced power, poor fuel economy, and increased emissions.
Another symptom of a bad coil is a rough idle. If your engine is idling roughly or stalling, it could be due to a faulty coil.
Additionally, a bad coil can cause your engine to run hot, which can lead to overheating and other serious problems.
If you suspect that your ignition coil is faulty, it's important to get it tested. Ignoring the problem can lead to more serious issues down the line, such as engine damage or failure.
By understanding the symptoms of a bad coil, you can take action before it's too late.