Have someone crank the engine and watch for a spark. Using a spark plug is a poor test of the ignition system. A screwdriver... with an insulated handle. They can be easily tested with a multimeter. The automobile had been around for at least 50 years when my 1930 Ford Model A was built, and guess what, it’s plug wires are just straps of metal from the distributor to the plugs. This video from Sears PartsDirect shows how to troubleshoot and fix spark plug and ignition problems, including using a spark plug tester to test the spark plug. Do not touch the tips of the test leads or the vehicle ground. Perform a spark plug wire resistance test. High voltage, as used in car ignition circuits, doesn't actually "go through" rubber insulation, it actually "walks" over the outside surface of the rubber to a grounded connection (you). If the plug was far enough away from metal nothing would have happened. If a spark jumps through the insulation to the screwdriver, the wire is bad. First Test: Spark Test. Then touch one to neutral or ground and one to the wire-under-test. HT leads are 'push fit' so require a firm pull to remove them from the plug – Don't pull the actual leads, as this can damage them, instead pull the rubber 'boot' as near to the spark plug as possible. With the introduction of coil-on-plug ignition, there is no long wire that is needed to connect a coil to the spark plug.. On engines that are equipped with a distributor or a remote coil pack, spark plug wires are used to transfer the spark from the coil to the spark plug. Doing this will unhook the kill switch, ignition switch, and all the wiring associated with those switches. The simple way I always check spark plug wires is to take a screwdriver with a good plastic handle and put an aligator clip lead on it with the other end of the wire grounded. If a one wire sparks well, but another does not, the system is weak; a weak spark or no spark means the magneto is at fault and should be replaced. Rest the wire back on the plug to prepare for load testing. I recommend that you use an HEI spark tester due to its accuracy and ease of use. Step 2: Test the wire. Build your own tester. The system is activated by the primary ignition system, most use a low voltage trigger system i.e. Now the whole wire and the coil that supplies it is loaded. So whether it's a Ford, a Chevrolet, a Mazda, a Suzuki, a Mitsubishi or whatever in the USA, or Europe or South or Central America, or where ever on the planet, these easy tests work. This fills a couple of useful needs--if you're getting ready to work on a circuit, you can see if power is flowing to it, and if you're trying to diagnose an electrical problem, you can use the tester screwdriver to see if power is indeed flowing to a non-operating device. Disconnect the wire from the spark plug and insert a metal screw- driver into the boot of the spark plug, which is the area that holds the spark plug. But worse than that, those misfires can destroy your catalytic converter. The plug terminals come with double-spring locks that make then resistant against vibration. Warnings . Some ignition wires have a copper core with small resistance. You can measure the resistance of the spark plug wires with a digital multimeter to see if they are working properly. On a separate note. Put the screwdriver in the unattached end of the plug wire, and hold the rest of the screwdriver near a metal surface. With a wire-testing screwdriver, of course. Use a digital or analogue multimeter (or ohmmeter) to check if the resistance of each spark plug wire is within the manufacturers’ guidelines. While trying to diagnose a tricky car not starting problem I was asked to check if the spark plugs were firing at all.. coil, wire and spark plug. 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