How to test a lawnmower coil with a multimeter, step by step


With the weather cleared, you want to start mowing your lawn. But as soon as you turn the key switch, the lawnmower won’t start! The first thought is that the problem is either with the battery or the lawnmower’s ignition coil. When you test the spark plug, it turns out that it won’t give a glimmer! So now, you are sure that the problem is with the ignition coil. You haven’t encountered this problem before and thus need a troubleshooting guide. If that’s the case, don’t worry because we are here to provide the solution to your problem by mentioning all the nitty-gritty tips and details you need to know.

How to test an ignition coil with a multimeter:

  • Step 1: Remove the ignition coil from the lawnmower
  • Step 2: Test the ignition coil using a multimeter
  • Step 3: Purchase a new ignition coil if the test fails
  • Step 4: Install the new coil
  • Step 5: Test the lawnmower with the new ignition coil

The lawnmower’s ignition coil is located inside the lawn mower’s engine and is attached to the fly wheel’s magnet. The starter coil’s service life may end due to its metallic body’s corrosion or if the lawnmower hasn’t been used for a long time. A lawnmower may have one or two ignition coils, which depends on the lawn mower’s number of cylinders. But the testing method for the ignition coil is the same independent of its number.  Below mentioned are the steps that help you not only to test the ignition coil but also to replace it:

We shall provide in-depth details of the steps mentioned above in the section below, like what sort of equipment to use for the testing, how to remove the ignition coil. Stay tuned to this article, as we are here to get your problem solved without wasting any time.

Step by step how to test lawnmower’s ignition coil:

The method below explains all the required steps to test the coil with a multimeter and replace it with a new one so that the lawnmower gets up and running again.

● Step 1. Remove the ignition coil from the lawnmower:

  • Step 1. Ignition coil location: The ignition coil is located inside the lawnmower engine and attached to the lawn mower’s flywheel magnet.
  • Step 2. Remove the plastic cover: First of all, remove the plastic covering from the lawn mower’s engine by loosening the screws with a screwdriver.
  • Step 3. Locate the ignition coil: Next, remove the engine cover located right above the gas tank. You should now see an ignition coil.
  • Step 4. Remove the lead: Remove the high-tension lead of the ignition coil from the spark plug and remove the spark plug from the lawnmower as well.
  • Step 5. Remove the kill wire: Remove the kill wire attached to the ignition coil with the help of pliers
  • Step 6. Take the coil out: The ignition coil can now quickly be taken out of the engine. Please remove it from the lawnmower to take it to the testing phase!

● Step 2. Test the ignition coil using a multimeter:

The ignition coil’s testing method is straightforward. All you need is a multimeter and the service manual for the engine used in the lawnmower.

  • Step 1: Set the multimeter to 20K resistance measurement mode.
  • Step 2: Now, look for the user’s manual of the service engine being used in your lawnmower. You can find one on the internet.
  • Step 3: Look for the ignition coil’s resistance/tolerance value table inside the user’s manual.
  • Step 4: Now, insert one end of the multimeter into the high-tension lead’s spark plug cap and place the other end of the multimeter on the coil’s base.
  • Step 5: The multimeter should give a resistance value within the range of the values given in the table present in the user’s manual.
  • Step 6: Now, place one end of the multimeter on the coil’s kill wire terminal and the other end on the coil’s base.
  • Step 7: Again, the multimeter should give a resistance value within the range of the values given in the table present in the user’s manual.
  • Step 8: Remember to look for specific values in the table when the multimeter terminals are placed on the ignition coil’s specific points.
  • Step 9: Similarly, place one end of the multimeter on the kill wire terminal and insert the other inside the spark plug cap and note down the resistance value.
  • Step 10: Suppose the multimeter gives values that are not in range of the values mentioned in the user manual’s table or gives no values at all. In that case, it means that your coil is faulty and needs a replacement.

● Step 3. Purchase a new ignition coil:

Now, as you have witnessed the test failure on the ignition coil, you finally decide that the option now is to buy a new one and throw the old one away! In doing so, you should take care that the new coil being purchased should be the same as the one being replaced. The critical thing to be kept in mind is whether one of your coils was faulty (if your lawnmower has two cylinders) or both. If both of the coils are faulty, then both of these must be replaced with new ones. Consulting the lawnmower’s user’s manual and getting the engine number for your specific lawnmower is also a good option in this process. During the purchase, always ask the seller to provide you the coil according to your particular model of the engine being used in the lawnmower.

● Step 4. Install the new ignition coil:

Are you tired after going through such a long process of testing and shopping? Don’t worry. You are almost at the point where your lawnmower gets up and running again. Just one more last step and that is to install the new coil into the lawnmower.

– Install the spark plug:

Firstly, you need to put the spark plug back in its place. Now, connect back the killer wire to the kill wire terminal of the ignition coil. Next, connect the spark plug cap off the coil to the spark plug. Place the coil’s screws back into their place, and tighten them just a little with the screwdriver’s help.  Here comes the most critical part of this installation process, so read it carefully! The distance between the coil and the magnet on the flywheel must be kept 10 points. So, for that, you can use a gauge and place it between the coil and the magnet, and then tighten the coil’s screws completely. Don’t have a gauge? Don’t worry; we have a pro tip as well. The business card that we mostly have all the time in our pockets can also keep this distance. So, it can also be used to get the job done.

– Assemble the casings:

Moving further, install the engine covering and the plastic covering back and tighten their screws using a screwdriver. You are now ready to test the lawnmower as the testing installation process is now complete.

● Step 5. Test the lawnmower with the new ignition coil:

After all the day’s hustle, why not test the lawnmower and take it for a spin on your garden. Put the key back in and turn the ignition switch. Guess what? The lawnmower has started and is buzzing like it’s a new one! You can enjoy your day and make your garden even more beautiful.

RELATED QUESTIONS:

1. How can I verify whether the issue is with my lawnmower’s battery or the lawnmower’s coil?

When your lawnmower doesn’t start, two possibilities may have caused this. Either your lawnmower’s battery is dead, or the ignition coil needs to be replaced. To check if the issue is with the ignition coil, a small test can be performed without opening the lawnmower’s engine and removing the coil to check it using the method mentioned above.

For this, first, you need to remove the spark plug cap from the spark plug. Then remove the spark and hook it back up to the tension lead (the spark plug cap). Next, ground the spark plug against the lawnmower’s body and start the lawnmower. If you see a spark being produced from the spark plug, it means that the coil is perfect and does not need a replacement. So, the problem might be with the battery or some other thing in this case. But if no spark is produced, it implies that the ignition coil needs a replacement!

2. How can I test my lawnmower’s spark plug?

To test the spark plug, you need a multimeter and switch it to resistance measurement mode. Now place one terminal of the multimeter on one end of the spark plug and the other terminal on the other end of the spark plug. Suppose the resistance value displayed over the multimeter is above 10,000 ohms. In that case, your spark plug needs to be replaced, and if it’s below 10,000 ohms, then your spark plug is perfect and does not need a replacement.

Final Remarks:

If you want to mow your lawn but your lawnmower won’t start the ignition coil may be malfunctioning. But the lawnmower’s ignition coil can easily be removed, tested, replaced, and reinstalled at your home by reading this article. Your safety is also our topmost priority, so don’t forget to take certain precautions while performing the testing process. You must always wear work gloves before starting the process to protect you from unnecessary cuts. Besides, the wrench set and other tools must be used with great care and kept out of children’s reach. The magnet and the ignition coil also need to be cleaned after some time to remove any dirt or carbon to increase the coil’s life. Finally, don’t forget to perform timely maintenance of the lawnmower’s other parts such as filters, cutting blades, and oil.

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