If you don't have your car's service manual, or you have after-market wires, you can usually find this information online. Plug one of the multimeter leads into the ground/earth terminal (the hole at the top) and the other into the left terminal. Connect the black multimeter test lead (using the appropriate tool) to the wire that connects to terminal #1 of the ignition coil connector. Include your email address to get a message when this question is answered. How do I change spark plug wires on a Chevy 2.2 engine? Inspect the boots on both ends for any damage and inspect the terminals for any corrosion or perhaps they are not holding tightly onto their connections. How to test spark plug wires. 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. This article was co-authored by Mike Parra. Now take the other wire end and repeatedly touch and disconnect it from the remaining battery terminal. For the domestic wire a good reading is no greater than 12,000 ohms per foot. Multimeter Test: Continuity. As a visual inspection you can look at the wires for any cracking, cut, scraped, or burned exterior casing. Make sure it matches the resistance in the manual. First just a cross section cut, you can see the internal components but it doesn’t give a good representation, so I’ll do a cross cut instead. The pinouts necessary to test these power connectors with a multimeter can be found in our ATX Power Supply Pinout Tables list. Thank you.". Individual coils for each cylinder that attach with a spark plug wire, similar to the LS motors used on Chevy and GMC trucks, can also follow this method. An Ohm meter, which is part of a multimeter, can only check a spark plug for a short circuit or a breakdown of insulation resistance. These are an inductive wire instead which has must less resistant than compared to the carbon core wires. Turn the power on and read the meter. And finally the carbon impregnated fibreglass core, where the electricity flows. Yes, although that can be caused by a variety of problems. Place one probe on either end of the wire touching the metal contacts, and look at the ohm meter to see the resistance. This article was co-authored by Mike Parra. This article reassured me that I am on the, "I like the spark plug leads checking method. Step 1. Get expert advice. Some manufacturers do this to cancel out magnetic fields. Some engines have coil-on-plug (COP) configurations that bypass the spark plug wires completely, although a boot is still present. An absence of spark will require replacement of the spark plug. AC is marked by a little wave and DC is displayed with three dots under a straight line. When exposed to heat and vibration, the carbon in the wire may loosen and reduce the conduction of the wire. A good spark plug should show an open circuit between the center electrode and the tip. Break the circuit, then touch the red probe to the wire from the power source and the black probe to the wire going to the load to close the circuit. Do I need to change the wires when I change the plugs? Scorch marks signal damage due to high heat from the engine compartment. It carries the high voltage (30k to 50k volts) produced by the ignition coil to the spark plug. Failed emissions tests due to elevated hydrocarbon emissions or a fault code indicating cylinder misfire. In a darker environment or at night, while the engine is running, you can also inspect for the wires leaking which would be shown by a spark and an audible tick or click. This article has been viewed 410,743 times. [1] There are two cases in terms of readings when you check a wire through a multimeter. Any resistance at all would mean the plug is bad. This can be a problem if you have had your spark plugs changed and the boots get put back on in the wrong order. % of people told us that this article helped them. If you really can’t stand to see another ad again, then please consider supporting our work with a contribution to wikiHow. You can first check to make sure that the plug wires and caps are all intact. Can damaged spark plug wires cause a car to jerk at low speeds? This may vary between manufacturers and will also depend on what type of environment they’re exposed to. Place the red probe on the live cable, and the black cable on the neutral and the reading will appear on the screen. Be sure to hit that SUBSCRIBE or FOLLOW button. Select the maximum range to get an accurate reading. This article has been viewed 410,743 times. He is ASE (Automotive Service Excellence) certified, has an AA degree in Automotive Repair Technology, and has over 20 years of mechanic experience. Step 5: Test the secondary circuit of the ignition coil. If everything is okay, the wires should be carrying a voltage of 230V, though it can be slightly higher or lower. Rewind the rope around the flywheel and turn the lawn mower's ignition switch on. We are looking at 940 ohms. What can I do? Testing spark plug wires with a multimeter (ohms) ... Ok I've searched around the forums and on the web and I'm getting conflicting info on how to test the spark plug wires. Connect your multimeter to the positive terminal or pin of your coil, and to the high output terminal that goes to the spark plug. Over time spark plug wires will wear out, causing various engine operation issues such as hard starting, misfires, rough idling, poor performance, poor fuel economy, and improper combustion burn. Mike Parra is a Master Mechanic in Arizona. Select "amps" on the dial. To do this, disconnect the main electrical connector coming out of the engine. If you suspect that your spark plug wires are damaged, you may be able to spot the problem yourself. You can also put the black Wire on the earth wire and the red on the Live Wire; you will still get a reading. Results. Mike Parra is a Master Mechanic in Arizona. Refer to the repair manual for import plug wire specifications. Setting the multimeter to the ohms sitting to measure resistance, on the 20k setting which will show us values in the 10,000 range. A spark plug wire is a basic but critical engine component. A multimeter is a small and inexpensive portable tool made to test electrical wiring and all types of home appliances. Select the voltage (V) … Do not assume that crossing spark plug wires is a bad sign. If you are having a no-spark problem, a good place to start after ruling out shorts, grounds, switches and spark plugs, is the ignition coil, spark plug caps and wires. Therefore, it is always advisable you switch off the breaker on the signal that you are running the test on to avoid any possible severe damages. The insulation stopping any voltage leaks. To ensure everything is all set, you might want to test the multimeter on a real live wire you are sure is working. Technically, a break is a full resistance that interferes with the flow of current through the wire. Test the wire from end to end with the leads of the meter. Have someone else rev the engine while you continue to look at it. Plug longevity varies with the "type" of plug (copper core, platinum, iridium etc.). If you have a manual for your vehicle, check there for the answer. To test the continuity setting’s calibration, touch the 2 terminals together and hold them in place. Keep in mind these are generic values and may vary between vehicle manufacturers and spark plug wire manufacturers. The first step in testing a wire is to select the correct voltage on your multimeter; AC or DC. The easiest way to test your spark plug wires is by using an ohm meter to measure resistance. 2. For tips on how to check the spark plug wires by inspecting the engine, scroll down! Touch the test probes together to determine the existing resistance in the test leads, then hold one test probe on one terminal, the other probe on the other terminal, this wire show’s 10,000 ohms, which by generic specs is good. To the metal armature part of the ignition coil, connect the negative lead of the ohmmeter. Case 2: If the display screen reads zero, then there is no voltage in the wire. Insert the spark plug probes into the correct sockets of the multimeter. ", https://www.popularmechanics.com/cars/how-to/a82/1272351/, https://www.yourmechanic.com/article/how-to-check-spark-plug-wires-by-robert-tomashek, https://axleaddict.com/auto-repair/Checking-spark-plug-wires-using-two-simple-strategies, http://www.zr1specialist.com/HAT%20Web/facts%20and%20failures/spark%20plug%20carbon%20track.htm, Testare i Cavi delle Candele di un'Autovettura, consider supporting our work with a contribution to wikiHow. Case 1: if the display screen reads zero, then please supporting! Wires normally last to about 100,000 kilometres or 60,000 miles connector coming of! The page 2 feet in ohms a tune-up, and devices about kilometres! Volts ) produced by the ignition coil the continuity setting ’ s calibration touch... This wire is about 2 feet in ohms and you may be able to spot problem... 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