There are 3 normal reasons for the ignition coil to fail. This is not very common on a small motor as the motor usually stops before the coil fails, but it is possible. Problems with resistance. If the wrong spark plug is used, ignition coil failure is to be expected.
The main cause of premature ignition coil failure is a worn or defective spark plug. A faulty spark plug wire has much higher resistance than normal. Due to this high resistance, a very high voltage is generated from the secondary windings of the ignition coils.
If you don’t see a spark, there is an ignition problem. Remove a spark plug lead and insert an old spark plug or spark plug tester into the end of the lead (socket). Place the spark plug on a metal surface of the engine or connect the spark plug tester to the engine. Then start the engine to look for a spark.
The mower may have a defective coil, especially if the mower cannot be started while it is still hot. If you have to wait for the lawn mower to cool down before starting it, you will probably need to replace the ignition coil.
If you try to start the engine and hear repeated squeaks, there is likely engine damage caused by a faulty ignition coil. You can still drive your car, but you will hear a lot of weird noises and even hear a snap when you accelerate.
The spark plug is clogged and shorted to ground or opens and the magnet, which works normally, cannot ignite it. A typical poor grip causes an immediate drop in abdominal control by 250 rpm or more. The main indicator is the sudden drop. You tried to bend over and clean the grip, but with no luck.
You have to put an ammeter in series with the coil and the 6 volt battery. A 6 volt coil consumes 4 amps. If you have an accurate ohmmeter, the reading on a 12 volt coil should be around 3 ohms. A 6 volt coil is about half that.
The only safe way to test a spark is to use a spark plug tester. If you suspect a coil problem, measure the primary and secondary resistance of the coil with an ohmmeter. If any of the specifications are empty, the coil must be replaced. A coil can easily be tested with a 10 megohm impedance digital ohmmeter.
Loss of spark is caused by something preventing the coil voltage from jumping through the electrode hole at the end of the spark plug. Think worn, cracked or damaged spark plugs, faulty ignition wires, or a broken manifold.
Connect the multimeter to the positive or pin on the coil and to the high power terminal leading to the spark plug. Most ignition coils should have a secondary resistance of 6000 to 10,000 ohms, but check the manufacturer’s specifications for the correct range.
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Place the ignition coil on a work surface. Set the knob to an ohmmeter or 20k ohm multimeter. Connect the positive lead of the ohmmeter to the socket or metal bracket on the spark plug lead. Connect the negative lead from the tester to the metal mounting part of the ignition coil.
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