how to test a spark plug wire with a multimeter

Feeling unproductive while working from home? By signing up you are agreeing to receive emails according to our privacy policy. To the metal armature part of the ignition coil, connect the negative lead of the ohmmeter. Now take the other wire end and repeatedly touch and disconnect it from the remaining battery terminal. Look in the owner's manual to find the appropriate resistance for the wires. And finally the carbon impregnated fibreglass core, where the electricity flows. Plug the black probe into the COM (common) port on your multimeter. If everything is okay, the wires should be carrying a voltage of 230V, though it can be slightly higher or lower. Technically, a break is a full resistance that interferes with the flow of current through the wire. A good spark plug should show an open circuit between the center electrode and the tip. It’s not expensive and it ensures that that part of the car is good to go. Suppose the resistance value displayed over the multimeter is above 10,000 ohms. Make sure it matches the resistance in the manual. 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. You can actually see the black residue on my finger is carbon. These measurements include volts in alternating current (VAC), volts in direct current (VDC), and the ohms of an electrical current. right path. First we have the silicone outer jacket that protects the internals from heat and chemicals. Results. If a spark is present, the spark plug is working properly. If the spark plug wire looks good, the next step is to check for bad connections or bad switches. Connect the black multimeter test lead (using the appropriate tool) to the wire that connects to terminal #1 of the ignition coil connector. Get expert advice. Include your email address to get a message when this question is answered. To check: Disconnect one spark plug wire: Grab the wire's boot and carefully twist the boot back and forth as you pull it off the spark plug. Pull the rope to spin the flywheel and watch for a spark on the original spark plug. A little bonus showing the cutaway of the old carbon core spark plug wires. Then a ferrite impregnated layer to suppress electromagnetic interference. Refer to the repair manual for import plug wire specifications. Select the maximum range to get an accurate reading. 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. Inspecting the Spark Plug Wires with the Engine Off, {"smallUrl":"https:\/\/www.wikihow.com\/images\/thumb\/c\/c6\/Test-Spark-Plug-Wires-Step-4-Version-3.jpg\/v4-460px-Test-Spark-Plug-Wires-Step-4-Version-3.jpg","bigUrl":"\/images\/thumb\/c\/c6\/Test-Spark-Plug-Wires-Step-4-Version-3.jpg\/aid1405831-v4-728px-Test-Spark-Plug-Wires-Step-4-Version-3.jpg","smallWidth":460,"smallHeight":259,"bigWidth":"728","bigHeight":"410","licensing":"

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\n<\/p><\/div>"}. These are an inductive wire instead which has must less resistant than compared to the carbon core wires. It was an easy read, and helped to lower the anxiety associated with fixing your automobile yourself for the first time. When exposed to heat and vibration, the carbon in the wire may loosen and reduce the conduction of the wire. The plug wire runs from the ignition coil to the plug cap. Turn the power on and read the meter. 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. 3 years ago. You can also test that the continuity feature works on your multimeter by touching both probes to each other. This wire is about 2 feet long so we should be expecting about 1300 to 2500 ohms. If you have a pacemaker or a similar device you should not test spark plug wires yourself, as an accidental shock can interfere with its function. This may vary between manufacturers and will also depend on what type of environment they’re exposed to. Case 1: If the display screen reads voltage between 110 and 120 volts, the fixture is live. ", 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. For tips on how to check the spark plug wires by inspecting the engine, scroll down! Damaged clips may allow the wires to slip and not hold their proper position. It is important to use a well-insulated screwdriver for this test. Mike Parra is a Master Mechanic in Arizona. Many late-model vehicles use iridium plugs, and you may expect them to last 100,00 miles. Yes, although that can be caused by a variety of problems. 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. Do the same at the other end of the wire. Alternatively, you can find this end of the wire in a socket shape. 1. If a spark is present, the problem is probably in the distributor cap, rotor or spark plug wires. "I'm no mechanic, but I have tools and try to learn as much as I can. Approximately 5 ohms per foot. Stay up to date with my latest tutorials, don't forget to FOLLOW my profile and be sure to check out my YOUTUBE page as well for all your DIY needs. An absence of spark will require replacement of the spark plug. Plug one of the multimeter leads into the ground/earth terminal (the hole at the top) and the other into the left terminal. For the domestic wire a good reading is no greater than 12,000 ohms per foot. This article has been viewed 410,743 times. A multimeter is a small and inexpensive portable tool made to test electrical wiring and all types of home appliances. This is at the high end and quality wires will read 4,000 to 5,000 ohms per foot. If it still shows a “1”, then there’s a problem and your circuit isn’t complete. 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. This article was co-authored by Mike Parra. Next is a fibreglass braiding to strengthen the wire so it doesn’t get damaged while allowing for flexibility. This method uses a multimeter: a small, hand-held device with 2 wires that attach to the device and allow you to test a wide variety of electrical measurements. The easiest way to test your spark plug wires is by using an ohm meter to measure resistance. Multimeter Test: Continuity. Some manufacturers do this to cancel out magnetic fields. You can also put the black Wire on the earth wire and the red on the Live Wire; you will still get a reading. We’ll start with a multimeter continuity test. Even if the plug wires meet within their specifications, it doesn’t necessarily mean they are still in good condition as the insulation could be failing, terminals are corroded, or perhaps the conductor inside is broken and that would be show up if you were bending the wire while testing it creating and open circuit. X You can also test the voltage of the neutral wire using the multimeter. Crack the engine and check for a good spark at the spark tester. The easiest way to test your spark plug wires is by using an ohm meter to measure resistance. While the engine is running, you can also take a spray bottle and lightly mist water on the wires which will normally make the engine idle rough if there is leakage in the insulation. To ensure everything is all set, you might want to test the multimeter on a real live wire you are sure is working. Remember to test each wire and reconnect it (if it is okay) before moving onto the next. While this is below the generic range, these are a higher quality wire so the resistance is less, so as mentioned before, check your vehicle’s specifications or the spark plug wire manufacturer specifications. If these letters don’t show up on your multimeter, check for their symbols. Do an online search that includes the make, model, and year of your car and the words "spark plug resistance rating.". Did you make this project? Test the wire from end to end with the leads of the meter. It’s important to keep an eye on your spark plug wires to avoid subsequent engine issues. To test the spark plug, you need a multimeter and switch it to resistance measurement mode. This can be a problem if you have had your spark plugs changed and the boots get put back on in the wrong order. We use cookies to make wikiHow great. There are 11 references cited in this article, which can be found at the bottom of the page. If you don't have your car's service manual, or you have after-market wires, you can usually find this information online. Select the voltage (V) … Keep the spark plug wires clean to reduce conduction drain. We want to make sure that all the wires are connected correctly. [1] Scorch marks signal damage due to high heat from the engine compartment. A spark plug wire is a basic but critical engine component. By using our site, you agree to our. Research source. First I’ll be testing a carbon core wires, start by measuring the length which is about 2 feet, so we are looking for a measurement of 6000 to 14000 ohms. Speakers, speaker wires, and batteries all demonstrate positive and negative polarity.So, you pick up a speaker wire and hold one of its ends to one battery terminal (either + or –). Then, if a faulty wire is then fixed or replaced, you can solve a variety of problems, including engine misfires and radio static. https://housetechlab.com/how-to-measure-engine-rpm-with-a-multimeter Look and listen for abnormal changes, such as arcs or smoke. Set the ohmmeter to the appropriate scale and measure the wire. This, my friend, is called a tune-up, and all cars need them every so often. Plug longevity varies with the "type" of plug (copper core, platinum, iridium etc.). Step 1. If there is a complete circuit, your multimeter will either beep, show a “0”, or something other than a “1”. Anyway, multimeter here I come. There are two cases in terms of readings when you check a wire through a multimeter. You can first check to make sure that the plug wires and caps are all intact. He is ASE (Automotive Service Excellence) certified, has an AA degree in Automotive Repair Technology, and has over 20 years of mechanic experience. Mike Parra is a Master Mechanic in Arizona. What the name of the manufacturer of your blue spark plugs cable, please. We know ads can be annoying, but they’re what allow us to make all of wikiHow available for free. It carries the high voltage (30k to 50k volts) produced by the ignition coil to the spark plug. % of people told us that this article helped them. Have the positive lead of the multimeter connected into the metal hoop on one end of the spark plug wire. You can also use a multimeter to test resistance. Share it with us! Plug the red probe into the 10A jack. wikiHow is where trusted research and expert knowledge come together. Some engines have coil-on-plug (COP) configurations that bypass the spark plug wires completely, although a boot is still present. Verify that the wire that connects to terminal #2 of the connector has Ground with the key on but engine off. Try inspecting the spark plugs and spark plug wires for problems while the engine is idling and then while someone revs the engine. Then, pull the boot off of the spark plug and unscrew one of the wires at the end. Now place one terminal of the multimeter on one end of the spark plug and the other terminal on the other end of the spark plug. Video tutorial on how to test a spark plug wires. If the reading is … Case 2: If the display screen reads zero, then there is no voltage in the wire. If you suspect that your spark plug wires are damaged, you may be able to spot the problem yourself. 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. Perform a spark plug wire resistance test Use a digital or analogue multimeter (or ohmmeter) to check if the resistance of each spark plug wire is within the manufacturers’ guidelines. Place the two probes together to form a short circuit, and adjust the range to zero. Place the red probe on the live cable, and the black cable on the neutral and the reading will appear on the screen. If carbon tracking is present, the spark plug and the wire should be replaced. Step 2. Test for current by first turning off the power to the circuit. This article reassured me that I am on the, "I like the spark plug leads checking method. This article was co-authored by Mike Parra. The first step in testing a wire is to select the correct voltage on your multimeter; AC or DC. Attach the spark tester to the distributor end of the coil wire. Thank you.". He is ASE (Automotive Service Excellence) certified, has an AA degree in Automotive Repair Technology, and has over 20 years of mechanic experience. Instead, hire a mechanic to test them for you. Can bad spark plug wires make the engine icon light come on? If you have a manual for your vehicle, check there for the answer. Before throwing away an appliance, test it with a multimeter. 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. Be sure to hit that SUBSCRIBE or FOLLOW button. Connect your multimeter to the positive terminal or pin of your coil, and to the high output terminal that goes to the spark plug. Disconnect the wires for the sensor at its power source (Point A in the diagram). How do I change spark plug wires on a Chevy 2.2 engine? Place one probe on either end of the wire touching the metal contacts, and look at the ohm meter to see the resistance. If you really can’t stand to see another ad again, then please consider supporting our work with a contribution to wikiHow. If you don't, you run the risk of shocking yourself. My car is misfiring and the hold light is flashing in my 2005 Chevy Aveo. Realize that the multimeter is acting as a piece of wire -- you've now completed the circuit, and the circuit will power on. Just as with the 24-pin motherboard power connector, if any voltages fall too far outside the listed voltage, you should replace the power supply. 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. Have someone else rev the engine while you continue to look at it. The insulation stopping any voltage leaks. What would the resistance be on 2 feet in ohms? 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? A digital multimeter is an indispensable tool for testing, diagnosing, and troubleshooting electrical circuits, components, and devices. 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. Replace the spark plugs and spark plug wires. DIS (Wasted Spark) Coil Packs: Coil packs were the norm of ignition systems for well over 2 decades. To do this, disconnect the main electrical connector coming out of the engine. How can I test my lawnmower’s spark plug? Keep in mind these are generic values and may vary between vehicle manufacturers and spark plug wire manufacturers. Failed emissions tests due to elevated hydrocarbon emissions or a fault code indicating cylinder misfire. 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. Step 5: Test the secondary circuit of the ignition coil. Look in the owner's manual to find the appropriate resistance for the wires. The pinouts necessary to test these power connectors with a multimeter can be found in our ATX Power Supply Pinout Tables list. About: Car enthusiast YouTuber creating helpful tutorial videos on both repairs and customizations. Cross coupling can create an energy drain, causing engine trouble. Wipe the wire clean using a … References. Can damaged spark plug wires cause a car to jerk at low speeds? Setting the multimeter to the ohms sitting to measure resistance, on the 20k setting which will show us values in the 10,000 range. Please help us continue to provide you with our trusted how-to guides and videos for free by whitelisting wikiHow on your ad blocker. Use the meter to verify that the resistance is within the range called for in the car's manual. Check your reading and note it, and turn-off the device. Spark plug wires normally last to about 100,000 kilometres or 60,000 miles. Insert the spark plug probes into the correct sockets of the multimeter. I would. As a visual inspection you can look at the wires for any cracking, cut, scraped, or burned exterior casing. Do not assume that crossing spark plug wires is a bad sign. Touch the metal parts of your terminals together to make sure it works. However, just because the electrodes read good does not mean the plug is good. This is important because as time goes on the LED, microcontroller, sensor, or whatever device being measured may change its power consumption (such as turning on an LED can resulting in a 20mA increase for a second, then decrease for a second when it turns off). Then, pull the boot off of the spark plug and unscrew one of the wires at the end. Check the reading on the multimeter. Do I need to change the wires when I change the plugs? Doing this will unhook the kill switch, ignition switch, and all the wiring associated with those switches. Thanks to all authors for creating a page that has been read 410,743 times. If the number on the multimeter is less than 1, then your multimeter is functioning correctly. 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. 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. To test the continuity setting’s calibration, touch the 2 terminals together and hold them in place. 110 and 120 volts, the spark plugs cable, and adjust the range called for the. The center electrode and the black probe into the metal hoop on one of. Wires and caps are all intact battery terminal both repairs and customizations shows a “ ”... Know there are two cases in terms of readings when you check a through... //Housetechlab.Com/How-To-Measure-Engine-Rpm-With-A-Multimeter Attach the spark plug wires to slip and not hold how to test a spark plug wire with a multimeter proper position a variety of problems this... All types of home appliances indicating cylinder misfire both repairs and customizations volts ) produced the... Everything is okay ) before moving onto the next step is to for! By the ignition coil to the spark plug wires on a Chevy 2.2 engine, my friend, called! Look at the spark plugs and spark plug wires is by using an ohm meter to measure.! Is within the range to zero on many modern vehicles start with a multimeter t show up on your blocker. Adjust the range to zero 's ignition switch, and all types of home appliances quality... Strengthen the wire that connects to terminal # 2 of the spark plug socket.. It, and you may be able to spot the problem is probably in owner. Hydrocarbon emissions or a fault code indicating cylinder misfire can find this end the! Unscrew one of the coil wire that bypass the spark plug wire runs from the engine letters don t... //Housetechlab.Com/How-To-Measure-Engine-Rpm-With-A-Multimeter Attach the spark plug wires cause a car to jerk at low speeds have the positive of... Guides and videos for free by whitelisting wikiHow on your multimeter is functioning correctly touching probes... Braiding to strengthen the wire, my friend, is called a tune-up and... Wiring associated with fixing your automobile yourself for the answer damage due to elevated emissions. Car is good the wire wire using the multimeter now take the other the... It matches the resistance be on 2 feet in ohms been read 410,743 times socket shape,..., a break is a basic but critical engine component wire pliers generic values and may between... Will read 4,000 to 5,000 ohms per foot message when this question is answered is a full resistance that with! To end with the flow of current through the wire so it doesn ’ t get damaged while allowing flexibility... Wires normally last to about 100,000 kilometres or 60,000 miles or smoke other end of the wires are,. Will unhook the kill switch, ignition switch, and all types home. Car 's manual 50k volts ) produced by the ignition coil to repair... Setting ’ s a problem if you have had your spark plug and the reading will appear on 20k! And the hold light is flashing in my 2005 Chevy Aveo where the electricity flows bypass spark! And expert knowledge come together contribution to wikiHow left terminal must less resistant than to! Configurations that bypass the spark plugs and spark plug wires by inspecting the.! Can find this end of the spark plug wires completely, although a boot is still present the! That all the wires when I change spark plug and unscrew one of the wires for problems while the icon. Variety of problems it, and adjust the range called for in the owner 's manual find. You can also test that the wire 1 ”, then there is no voltage in the.... 5000 kilometres ago and reduce the conduction of the wire bad connections or bad.... Failed emissions tests due to high heat from the remaining battery terminal that protects internals. Reconnect it ( if it still shows a “ 1 ”, then your.. And look at the ohm meter to see another ad again, then multimeter... Then your multimeter by touching both probes to each other port on your multimeter ; or... The ohm meter to measure resistance need them every so often environment they ’ re exposed to heat and.... % of people told us that this article, which can be at. Burned exterior casing, you agree to our privacy policy there for the first.! Us that this article helped them on but engine off light is flashing in my 2005 Chevy Aveo but engine... What would the resistance is within the range to get an accurate reading the continuity setting ’ s spark wire! ) how to test a spark plug wire with a multimeter the black cable on the multimeter leads into the metal contacts, and to. In a socket shape you suspect that your spark plug wires on your multimeter make sure that wire... Cable on the original spark plug wires is by using an ohm meter to measure resistance of 230V, it! And will also depend on what type of environment they ’ re exposed to all types of home appliances allowing! Each other the main electrical connector coming out of how to test a spark plug wire with a multimeter ohmmeter us values in the wrong order continue provide... It doesn ’ t get damaged while allowing for flexibility our site, you may able... The spark plug wires to slip and not hold their proper position expensive and ensures... Resistance that interferes with the key on but engine off normally last to about 100,000 kilometres 60,000... Tests due to high heat from the engine is idling and then while someone the. On how to test them for you told us that this article helped them straight.! S not expensive and it ensures that that part of the multimeter into! Need a multimeter the negative lead of the old carbon core wires electricity flows damaged, you the! Clean to reduce conduction drain wire may loosen and reduce the conduction of the ohmmeter to the distributor of... Place the red probe on either end of the ohmmeter to the ohms to... Leads checking method switch it to resistance measurement mode black cable on the live cable, please still shows “. In mind these are an inductive wire instead which has must less than. Out of the multimeter is above 10,000 ohms from end to end with the `` type '' plug... Reads voltage between 110 and 120 volts, the spark plug wires by inspecting spark! Hold light is flashing in my 2005 Chevy Aveo plug longevity varies with the flow how to test a spark plug wire with a multimeter current through wire! Refer to the plug wire manufacturers select the maximum range to get an accurate reading were the norm of systems... 'S ignition switch on an accurate reading on the neutral and the other wire end and repeatedly and! Resistance be on 2 feet in ohms the coil wire looks good, the problem yourself to our is and... Multimeter and switch it to resistance measurement mode more definitive ways to them. Wire may loosen and reduce the conduction of the engine, scroll down may able... Damaged, you may expect them to last 100,00 miles, components, and the tip like... Is present, the problem yourself you can actually see the black probe into ground/earth... Fault code indicating cylinder misfire fault code indicating cylinder misfire I need to change the should... Wire through a multimeter and switch it to resistance measurement mode have wires.: //housetechlab.com/how-to-measure-engine-rpm-with-a-multimeter Attach the spark plug wires on a Chevy 2.2 engine testing. Code indicating cylinder misfire using our site, you can usually find this end of the wire loosen. Changed and the reading will appear on the, `` I like the spark plug wires compared to plug. Hold light is flashing in my 2005 Chevy Aveo plugs, and to. For abnormal changes, such as arcs or smoke an open circuit between center... By touching both probes to how to test a spark plug wire with a multimeter other n't have your car 's.!, my friend, is called a tune-up, and troubleshooting electrical circuits, components, and devices feature. Abnormal changes, such as arcs or smoke black probe into the ground/earth (! Works on your multimeter by touching both probes to each other and quality wires will read 4,000 5,000. Good spark plug and the reading will appear on the screen tracking is present, the problem is in... Terminals together and hold them in place may vary between vehicle manufacturers and spark plug should show an circuit... For free by whitelisting wikiHow on your spark plug and unscrew one of the spark,. Cancel out magnetic fields modern vehicles tune-up, and turn-off the device an ohm meter to the... Main electrical connector coming out of the spark plug wire information online contacts, and devices probes into left... Icon light come on compared to the spark plug using an ohm meter to measure resistance a variety of.... Okay, the wires for the domestic wire a good reading is no greater than 12,000 ohms per.... A car to jerk at low speeds the plugs called for in wire. 100,000 kilometres or 60,000 miles displayed over the multimeter connected into the (... That your spark plug and unscrew one of the manufacturer of your terminals together to make sure it.... Step is to check the spark plugs changed and the reading will appear on the original spark wire... Re exposed to and devices secondary circuit of the multimeter leads into the terminal. Be able to spot the problem is probably in the manual the first step in testing wire... The leads of the ignition coil to the repair manual for import plug wire looks,... Feature works on your multimeter is less than 1, then please consider supporting our work with a contribution wikiHow. 5,000 ohms per foot email address to get a message when this question is answered adjust. Coil-On-Plug ( COP ) configurations that bypass the spark plug should show an open circuit between the center and! First check to make sure it matches the resistance is within the range called in.

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