How to Test a Lawn Mower Coil
The convenience of a quick setup is an appreciated quality of a gas-powered lawn mower. There is no need to find all the extensions and plug each into its respected position, only to hope that the extensions will reach across the entire lawn. All that needs to be done is to fill up the fuel tank and start the engine.
However, when a gas lawn mower gets older or has done its fair share of hard work, it can become troublesome to get the mower to start. Ignition failure is a common problem, but it does not have to ruin your day. Knowing the correct procedures of fault tracing and how to solve these problems will go a long way.
The most common occurrence is a faulty spark plug. If it has been determined that the spark plug is not the source of the fault, it might be the coil or other electric faults. If it is clear that the coil cable has no observable faults, like worn points, tears, or anything obvious, then you will have to test your coil.
Here we look at exactly how you can do that without much difficulty so you can get your lawn mower back in action as soon as possible. So, let's get right to it.
What You Will Need
You may already have all of the needed hardware to reach the coil, which would probably include screwdrivers and wrenches. This is if the coil is located somewhere beneath all the engine covers. In most models, this will be the case, but some manufacturers might place the coil a good distance away. It may be mounted in an easily accessible location somewhere on the body of the mower.
If you have positively identified the coil and removed all the necessary covers and obscuring components, then you will need access to electrical testing equipment. This could be anything that has the ability to test for resistance in an electrical current or device. The most common type of device you will find is a multimeter.
Alternatively, you could also use a tester that only measures resistance. In some cases, these can give you a more accurate reading than many multimeters. A resistance tester is specifically called an Ohmmeter. With the Ohmmeter or multimeter ready and the coil exposed, you can begin the testing process.
How to Test a Lawn Mower Coil
A few precautions should be taken before the test can begin. Always practice safety and keep clear of any moving parts. This will include the flywheel, which in many models will be located so that it is in touch with the coil’s armature.
If the lawn mower is an older model that still uses a breaker point coil, this will not be the case. Consult the manual for manufacturer-specific information, as well as the correct procedures for accessing the coil. If everything is ready, set the multimeter to Ohm readings.
In some testers, this will require placing the red lead terminal in the socket marked for this specific task. If uncertain, consult the meter’s instructions leaflet. If you are using an Ohmmeter, this procedure should not be necessary. The socket would usually be marked with the Ohm sign, which looks like an awkward horseshoe ( Ω ).
Observing the coil, you should see two terminals. One will have a cable leading to the spark plug, and the other will lead to an earthing point. Use the red or positive testing probe by placing it inside the spark plug housing. The black or negative probe should be touched to the other terminal plate extending from the coil.
Make sure that the engine switch, if one is present, is turned on so that current is flowing to the coil. Otherwise, you will get a 0-rated reading, making you think that it might be defective.
For the same reason, the coil’s earth wire should be detached to prevent any shortening. Give the meter a few seconds to get a final reading. It should give a reading ranging between 0.5 Ohms to 1.3 Ohms to indicate that the coil is operating as it should. If the reading is zero, despite the fact that current is flowing, then the coil is dead and needs to be replaced or fixed. If it reads below 0.5 Ohms, the coil is defective.
If neither the spark plug or coil is defective, the problem could be with the battery. A defective coil does not necessarily need replacing. In some cases, it can be repaired. Have it inspected by an electrician with the correct expertise, specifically an auto electrician or even at a local hardware store that offers such services.
For a more accurate and detailed insight into your lawn mower, check the manual or visit the manufacturer’s website for more information. And if you are still coming unstuck and can't work it out for yourself, it is always best to seek out a professional who can help you out.