How to test stihl ignition coil with multimeter

Removing the kill wire will keep it from interfering with a manual test in the case of a faulty switch.

Warning

When testing a warm engine on any two-cycle product, be careful not to touch any engine part due to a burning hazard.

Maintain your Stihl tool so it will provide reliable service.

Stihl makes several types of equipment that withstand high usage for professionals or homeowners who require extra power, dependability and longevity of their power tools. Engines on Stihl trimmers, chainsaws, blowers, edgers and cultivators are two-cycle. A faulty ignition coil will disable any two-cycle engine from starting because it will not allow the sparkplug to operate. Small engines need spark, fuel and air to start and run, so testing is of the utmost importance.

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Automotive Coil Tester Method

Step 1

Place the Stihl tool on a sturdy work surface. Start the test with either a cool or a warm engine.

Step 2

Attach an automotive coil tester by placing the end of the tool with grooves over the sparkplug wire. Do not disconnect the wire from the sparkplug. Crank the Stihl equipment.

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Step 3

Watch the coil tester when cranking the equipment. If a light flashes inside the tool, there is sufficient spark in the sparkplug, indicating that the ignition coil is working properly. If the light does not flash inside the tool, the ignition coil needs replacing.

Sparkplug Method

Step 1

Remove any guard pieces that cover the Stihl tool by turning the screws counterclockwise with a Phillips screwdriver. There are one to two plastic covers over the engine area, depending on the tool.

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Step 2

Remove the sparkplug from its wiring harness by pulling it straight out. Disable the kill switch on the tool by unplugging it from its wiring harness. If you are not sure where the kill switch is on your tool, refer to your owner's manual.

Step 3

Open the top ground of a new sparkplug so that is has a large gap. Replace the starter guard pieces with screws so that nothing may enter the starter as it turns and you will not accidentally touch it. Pull the starting cord to start the Stihl engine.

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Step 4

Crank the engine and observe the end of the sparkplug. If you see a spark jumping the gap between the top of the sparkplug and the ground, there is sufficient spark. This result proves that the ignition coil is working.

An ignition coil gets used to transfer voltage signals to the spark plug to ignite the fuel and air mixture in the chainsaw. It will naturally become defective throughout its use, resulting in the need for a replacement part.

In this article, we will dive into the procedures of testing a chainsaw ignition coil using a digital multimeter. We will also talk about all the required steps and other reasons why your chainsaw can’t start.

Table of Contents

• How to Test a Chainsaw Ignition Coil (Easy Steps)
  • Step 1: Take Some Safety Measures First
  • Step 2: Locate the Ignition Coil
  • Step 3: Disconnect and Test the Spark Plug
  • Step 4: Remove the Spark Plug
  • Step 5: Check primary & secondary Ignition Circuits of the Coil
  • Step 6: Disable Fuel Pump Fuse
  • Step 7: Crank the Engine
  • Step 8: Check for Blue Sparks
  • Step 9: Reinstall the Coil
• Reasons why your Chainsaw won’t start and how to Fix
  • 1. A Spark plug might be Defective
  • 2. A Clogged Carburetor
  • 3. The Ignition Coil might become Defective
  • 4. The Recoil Starter might be Defective
  • 5. The Chainsaw may have a Broken Rewind Spring
  • 6. The chainsaw’s engine is flooded with Fuel
  • 7. The Choke is Activated in warm Weather
  • 8. The fuel has Deteriorated
• Conclusion
• Multimeter Brands for Testing Chainsaw Ignition Coil

How to Test a Chainsaw Ignition Coil (Easy Steps)

Like any other machine, diagnosing and fixing your chainsaw requires several preparation stages to ensure safety and efficiency.

Preparation – Safety must come first

You will need the equipment in the list below to diagnose and fix this issue. It is advisable to take the machine to a technician or experienced professional if you are not handy. A chainsaw is a dangerous machine; if not properly handled and maintained, a tiny mistake can result in disastrous consequences.

• Gorilla Work Gloves
• Anti Fog Safety Goggles
• Spark Plug Tester
• Digital Multimeter

Step 1: Take Some Safety Measures First

Equip yourself with the above list of safety tools that is the gloves and safety goggles. A defective element may be expelled into the air in unpredictable patterns that may injure you. The safety measures are for your protection and help you be careful and gentle in your handling.

You will also have to wait till the engine has cooled down before you begin your diagnosis. Additionally, the chainsaw engine needs to get turned off to avoid any electrical issues and mechanical complications.

Step 2: Locate the Ignition Coil

The location of the ignition coil is near the carburetor, depending on the chainsaw model and manufacturer. The best way to find it without a treasure hunt is to look at the user manual that came with the chainsaw.

Pay attention to the diagrams and schematics in the user manual to locate the ignition coil. If you do not have the user manual, you can go to the manufacturer’s website to find a downloadable manual. In addition, most companies provide online PDF manuals for free, and if they aren’t available on their websites, you can typically contact them to send them to you.

Step 3: Disconnect and Test the Spark Plug

Some wires connect the distributor to the spark plug. Disconnect the spark plug from these wires using a few spark plug sockets and other wrenches. Then, proceed to test the spark plug with the spark plug tester. This gets done with the help of alligator clips that attach to the wires instead of the spark plug.

Turn On the engine and notice if there are any sparks between the tester’s gap. If any, the spark plug is defective and will need a new replacement part.

Step 4: Remove the Spark Plug

Altogether remove the spark plug from the chainsaw assembly using a spark plug socket. Proceed to use a cover on the open hole to prevent dirt and debris from entering the engine.

Step 5: Check primary & secondary Ignition Circuits of the Coil

There is a primary and secondary ignition circuit that make up the ignition coil of the chainsaw. You are going to use the multimeter to test both of the circuits. First, the primary circuit is tested by attaching the negative and positive ends of the multimeter terminals with the coil’s respective negative and positive terminals.

Typical readings range from 0.4 ohms – 2 ohms. Any other reading, a zero, less than the acceptable range, above the excellent range, will mean that the device has a short or open circuit. Regardless of the reason, any reading apart from the normal ranges will require you to replace the part.

For the secondary circuit, the normal ranges are 6000 ohms to 10000 ohms. You can test the circuit by attaching the positive end of the coil to the multimeter and attaching it to the high output terminal traveling to the spark plug. Any reading that deviates from the standard range will require a replacement part.

Step 6: Disable Fuel Pump Fuse

The purpose of disabling the fuel pump fuse is to make sure the engine does not start so that you can analyze the spark plug. Failure to do so will cause the cylinders not to fire since the spark plug is missing. The engine will also flood as a result of this. Therefore, disable the fuel pump fuse before going to step 7.

Step 7: Crank the Engine

Turn On the engine at this step if the ignition coil is working correctly. The purpose is to provide power to the system to check for blue sparks and perform further testing.

Step 8: Check for Blue Sparks

Blue sparks are an indication of an efficient and adequately functioning chainsaw. You may notice orange sparks or no sparks at all in case the issue wasn’t resolved. Orange sparks signify an insufficient supply of current to spark plugs, whereas zero sparks showcase a problem in the coil system; dead circuit or faulty connections.

You will need to restart the steps if you do not see blue sparks since there still is an underlying issue that isn’t yet addressed.

Step 9: Reinstall the Coil

You are done. If you followed the instructions to the 8, you have probably solved the ignition coil issue already. Proceed to place the coil back into the system and reattach all the wires and components to their respective orientations.

Reasons why your Chainsaw won’t start and how to Fix

Diagnosing a chainsaw that won’t start, especially when the underlying issue isn’t located in the ignition coil. If you have gone through all the steps, but the problem persists, your answer may lie in the following list of reasons:

1. A Spark plug might be Defective

A defective spark plug will not be able to create an electrical current that ignites the engine system. With that said, you can diagnose the spark plug by inspecting it for any dirt, damages, and cracks. Moreover, the spark plug can become defective if it has a faulty electrode or a massive carbon buildup. So make sure to replace the bad spark plug to fix the issue.

2. A Clogged Carburetor

A clogged carburetor is considered a bad one. A bad carburetor is mainly a result of fuel that has been left in the tank for too long. Over time, the fuel will get sticky and clog the carburetor. To fix this issue, clean the carburetor, remove the fuel, and use a cleaning agent to wipe the entire element clean.

3. The Ignition Coil might become Defective

To fix a defective ignition coil, you will need to get a new one since it is near impossible to fix it.

4. The Recoil Starter might be Defective

The issue may be the recoil starter itself, which means it went wrong or malfunctioned in some mechanical way. An excellent example of this is when the pulley system gets stuck, requiring you to put it back into its standard orientation. Replace the recoil starter if the pulley position isn’t the problem.

5. The Chainsaw may have a Broken Rewind Spring

A broken rewind spring will often cause the cord not to rewind after each pull. To fix this, all you will need to do is get a new rewind spring, which will sometimes require you to replace the entire recoil starter assembly. However, this will depend on your chainsaw model and manufacturer.

6. The chainsaw’s engine is flooded with Fuel

The engine can get flooded for various reasons, the first one being an incorrect ratio of petrol to oil. An improperly calibrated carburetor is also another reason since it affects the revolution speeds. Moreover, a wet or faulty spark plug can flood the chainsaw’s engine since it won’t create sparks.

7. The Choke is Activated in warm Weather

Activating the choke in warm weather will cause the engine to get flooded with gasoline. A flooded engine will cause the chainsaw not to start in mild or warm weather. The choke position helps increase the fuel and air mixture in the carburetor to pump up the fuel flow.

8. The fuel has Deteriorated

When in storage, the fuel will start to break down in almost a month, forming a residue that clogs the carburetor. To prevent this, make sure to empty and clean the gas tank monthly. You can also use a fuel additive like STA-BIL Fuel Stabilizer to maintain the freshness of the gasoline for months.

Conclusion

All the steps mentioned above will help you test the chainsaw ignition with a multimeter and maintain your chainsaw over time. In addition, you can take a few maintenance measures to keep it efficient and prolong its lifespan by:

How do I know if my Stihl coil is bad?

Can you test an ignition coil with a multimeter?

How many ohms should a ignition coil have?