There are two coils of wire, termed windings, within an ignition coil. In this tutorial I'm going to explain how to test the ignition coils on the 2002, 2003, 2004, and 2005 4.2L Chevrolet TrailBlazer and GMC Envoy. Automotive coil tester. To test the resistance of the coil in your chainsaw which is called a bench test, take your multimeter and remove the coil from your chainsaw to get easy access to its electrical terminals. Do NOT follow this link or you will be banned from the site! If the cylinder is misfiring, take a look at the following section for more testing suggestions: TEST 4: Other Common Misfire Causes. A safer way to test the ignition coil. Ignition coils take energy from the battery (usually 12 volts) and convert it to a high enough voltage (50,000 volts or more) to create a spark. The check engine light flashes when the misfire is occurring. It does not matter which lead goes where in this case. You'll see one or more of the following: Besides a misfire trouble code stored in your Chevrolet Trailblazer or GMC Envoy's fuel injection computer you're going to see one or more of the following symptoms: If your test results indicate that an ignition coil is defective on your 4.2L Chevrolet TrailBlazer or GMC Envoy then you should that take a look at the following links and comparison shop. Test the engine to see if it starts and runs correctly. The spark tester will do one of two things: Spark or Not Spark. The procedure for testing the coil is the same for every ignition coil out there, but if your car has coil packs, it may require a different procedure. Put the negative lead of the tester onto the metal armature portion of the ignition coil. The issue here is a coil that has worn out from the constant charging and discharging cycles. So when an ignition coil fails the very first thing that you're going to notice is a misfire problem when the engine is running. There are a lot of knock-off parts out there. Testing the ignition coil and the spark plug Connect the tester between the spark plug boot and the spark plug. On older-style coils these will be posts on the top of the coil. Sparkplug. He lives in Minneapolis, MN. The ignition coil provides the electrical current for ignition on a gas-powered lawnmower. The next step is to make sure it's getting power, for this test go to: TEST 2: Making Sure The Ignition Coil Is Getting Power. It converts the power from your car's 12-volt battery into the thousand or so volts that the spark plugs need in order to fire and then ignite the engine's air-fuel mixture. Either way, once the engine is started, the flywheel keeps turning, creating a self-perpetuated ignition cycle. This is a test result also confirms that this specific ignition coil is getting power and an activation signal from the fuel injection computer. Comparing the results to the manufacturer’s specifications is supposed … If you are willing to spend a little more, there are machines that can test ignition coils under use. Without this spark the end result is a dead cylinder that is not producing power. The 12-volt pole is the spot where the power comes into your coil. The majority of the ignition coils usually have a secondary resistance of about 6,000 to 10,000 ohms. Remove the ignition coil from the bracket or mounting block holding it in place. Lay the ignition coil on a work surface. You will need to test the ignition coil if your vehicle does not start, misses frequently or stalls after warming up. With many lawnmowers, this will be enough to expose the flywheel and ignition coil; with other mowers, you may need to remove some other shields or parts before you see the coil. The engine idles fine but breaks up under load. Some vehicle ignition systems use coil packs to convert the power from the 12-volt battery in your car to the necessary 35,000 volts required to fire spark plugs instead of a distributor and rotor assembly. It will be the part mounted near the engine flywheel and will have an insulated wire leading to the top of the spark plug mounted in the engine block. The ignition coil is usually hidden beneath the cover your lawnmower but is clearly visible when you take the motor cover off. This is the primary resistance, and it should read between .4 and 2 ohms on your Ford coil. Jeep  |   Before checking the ignition coil, ensure there is 12V going to the terminal 15 on the coil. It's impractical to uncover the coil and examine the wire; fortunately, there's an easier way to find a break -- a continuity test. A gap that is too wide or too narrow will not allow the ignition system to work properly. 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