How to Test a Chainsaw Coil with a Multimeter?

  • Post author:

Like any other piece of equipment with electrical components, chainsaws can stall abruptly. Technicians link the problem to several issues, including a clogged arrestor, defective spark plug, clogged carburetor, and a broken rewind spring. 

Although there are multiple issues that can make a chainsaw stall, technicians say that a faulty ignition coil is the most common issue. This part is responsible for converting electrical energy into a high-voltage spark that ignites the engine. 

For that reason, when troubleshooting a stalled chainsaw, it would make sense to begin with troubleshooting the ignition coil before proceeding to other areas.  If it is the first time your testing a chainsaw coil, this guide will walk you through the chainsaw coil diagnosis process.

5 Steps to Test a Chainsaw Coil with a Multimeter

At first, diagnosing your chainsaw’s ignition coil, especially if you are a first-timer, will look like a daunting task. You will be left thinking about where to find the chainsaw coil, tools to use, and the right process to troubleshoot the coil with a multimeter. But, the good news is, you can execute the process using the following steps.

1. Get the right Personal Protective Equipment

Testing a chainsaw can expose you to several hazards. Electrical parts like the spark plug can shock you, sharp parts like the cutter can prick your bare skin, gas fumes can irritate your airways, and some hot parts like the engine can burn you. Basically, without the right PPEs, you will be exposing yourself to several unforeseen injuries. 

To keep yourself safe throughout the troubleshooting process, it would matter to wear the right PPEs before you start testing. Some of the PPEs that will come in handy during the diagnostic process include safety glasses, leather gloves, dust masks, overall, and safety boots. 

Apart from wearing the right PPE, power off the chainsaw, and make sure that the engine has completely cooled before you proceed to test the coil. That way, you will not suffer burns from the hot engine, and the chainsaw cannot start unexpectedly.

2. Locate the Chainsaw’s Coil

With the right safety wear, proceed to locate the chainsaw’s coil. Since chainsaws are not universal, the location of the coil will differ from one chainsaw brand to another. Therefore, if you wish to eliminate guesswork, use your brand’s manual to locate the coil.

The manual will not only help you locate the coil, but many detailed manuals have a diagram that will help you access the part without fumbling around. If you misplaced the printed manual, download PDF manuals from the manufacturer’s official website or contact customer support and request them to send one.

For most chainsaws, the coil is located near the distributor. Therefore, if you cannot find your chainsaw’s user manual for some reason, unscrew the chainsaw’s top cover to access the coil. The part is often concealed under a plastic cover.

3. Disconnect and Test the Spark Plug

The spark plug is the first part you will encounter after opening the saw’s top cover. A rubber shroud covers the spark plug in many modern chainsaws. Some units might not have the shroud. Pull the shroud away to reveal the spark plug.

After removing the rubber sleeve, dislodge the spark plug wire from the end of the spark plug. Then, use an appropriately sized socket wrench or spark plug socket to unscrew the spark plug. Cover the cavity left behind by the spark plug with a dry piece of cloth to prevent debris, dirt, and dirt from clogging it.

To test the spark plug, set your multimeter to the ohms position. Touch the multimeter’s test leads together and ensure the meter’s display reads zero. Afterward, touch one lead to the spark plug’s terminal and the other to the engine ground. A working spark plug should have a maximum resistance of 12,000 ohms.

4. Detach the Ignition Coil from the Chainsaw Engine

After removing and testing the spark plug, test the ignition coil’s primary and secondary ignition coils. Since it would be hard to test the ignition coil while in its compartment, it would make sense to detach it from the chainsaw before you start testing.

Just like the spark plug, removing the ignition coil is straightforward. Use long-nosed pliers to dislodge the wire connector and harness clip from the engine.

Furthermore, use a screwdriver to remove the screw attaching the ignition coil to your chainsaw’s engine.
Again, since various chainsaw brands are created differently, use the user manual to help you remove the ignition coil for testing.

5. Test the coil’s primary and Secondary Ignition Circuits

A chainsaw coil has two ignition circuits—the primary and secondary circuits. You will have to test the two circuits separately to identify if anyone has an issue. To test the primary ignition circuit, set the multimeter to the ohms setting, and identify the circuit’s negative and positive terminals. In many chainsaws, the terminals are properly marked for ease of identification.

After identifying the primary circuit’s terminals, connect the multimeter’s positive test lead to the circuit’s positive terminal. As well, connect the multimeter’s negative test lead to the multimeter’s positive lead. The average resistance reading on your meter’s display should range from 0.4-2 ohms.

Nonetheless, you can refer to your user manual to get the expected good reading. If your multimeter readings are below 0.4 ohms or above 2 ohms that indicates that your chainsaw’s coil is faulty. You will need to replace it.
To test the secondary ignition circuit, place your multimeter’s positive test lead to the circuit’s positive terminal. On the other hand, place your multimeter’s negative test lead to the output terminal connecting to the spark plug. The normal readings will range between 6000-10,000 ohms. A reading of zero will suggest that your coil has a short circuit. You will need to replace it.

6. Replace the Faulty Coil and Conduct a Bench Test

A damaged chainsaw coil cannot be repaired. Therefore, if the multimeter test suggests that the spark plug, primary ignition circuit, secondary ignition circuit, or spark plug wire is damaged, you will have to replace the faulty coil with new original manufacturer equipment. Replacement parts are readily available in reputable online stores. 

Before installing the new part, run a test using your multimeter to ascertain that the new part is working correctly. Use your multimeter to test for resistance of the spark plug and the primary & secondary ignition circuits the same way you troubleshot the faulty coil.

After ascertaining that the chainsaw coil is in top working shape, insert the new chainsaw coil into the cavity where you removed the old chainsaw. Connect all its wires to the right terminals. 

Final Remarks

A chainsaw stalling is a common occurrence experienced by all lumberjacks and hobbyists. The problem can result from a clogged carburetor,low fuel , the spark plug is faulty, or the rewind spring is damaged. However, while there are several reasons why chainsaws can stall, technicians claim that a faulty chainsaw coil is a leading cause. This is why you are always advised to start troubleshooting your chainsaw from the coil whenever it stalls. If it is your first time doing it, and yet you lack the skill and confidence needed to test the coil using a multimeter, do not fret. Use your chainsaw’s manual to identify the location of the ignition coil. Wear appropriate safety gear, and open the chainsaw’s top cover to reveal the coil. With the right tools, dislodge the chainsaw’s ignition coil, and use a multimeter to test the spark plug, as well as the primary and secondary ignition systems. Replace the faulty coil with a newer unit.

Frequently Asked Questions

What is a chainsaw coil?

The chainsaw coil is a system that converts low current from the battery to a high voltage spark needed to ignite the fuel in a chainsaw’s engine compartment. Typically, a chainsaw cannot run when the ignition coil is damaged.

The chainsaw’s ignition coil has four parts—the ignition module, spark plug, armored wire, and flywheel with magnets. The flywheel has blades that rotate to cool down the engine. It acts as the chainsaw’s fan.

The ignition module switches the ignition coil on/off to help fire the chainsaw’s spark plug. The spark plug fires a spark that ignites the fuel in a chainsaw’s fuel compartment. The armored wire supplies a high voltage electric current from the ignition module to the spark plug.

How can you tell a chainsaw coil is faulty?

Since the coil ignites your chainsaw’s engine, a stalled engine would be the first indication that the coil is faulty. Moreover, a faulty coil can be characterized by loss of power, high fuel consumption, and hard starts.

As there are several reasons why a chainsaw can stall, lose power, consume more power, or experience hard starts, you would need a multimeter to test and prove if the coil is faulty.

What tools are needed to test a chainsaw coil?

A multimeter is not the only tool needed to diagnose the chainsaw coil. However, you will also need other extra tools like a spark plug wrench to remove the spark plug, screwdrivers to unscrew, and a spark plug tester to test faults in a spark plug. As well, you may need additional tools like long-nosed pliers.

How many Ohms does chainsaw coil have?

On average, a functional chainsaw coil should have a resistance ranging within 0.4-2 ohms. However, since each chainsaw is designed differently, it would be prudent to check your user manual to confirm your chainsaw coil’s exact ohms. The ohms figures might differ from one brand to another.

What are the other reasons why a chainsaw can stall?

Besides a defective chainsaw coil, a chainsaw can stop working for several reasons. Common issues you would encounter include a flooded engine, faulty recoil starter, lack of fuel, clogged carburetor, and damaged rewind spring. Therefore, if you have just tested your chainsaw’s coil and found out it is working properly, carry on troubleshooting the faults mentioned earlier.

Toby Ashby

I am an automotive specialist with over 20 years of experience in and around electronics