Champion Spark Plug Company’s Engineering Manual gives the nominal value for their resistor type of aviation spark plugs as 1000 - 1500 ohms (no +/- value is shown, but minus 400 and plus 1000 probably wouldn’t be … If the firing end of a spark plug is brown or light gray, the condition can be judged to be good and the spark plug is functioning optimally. Important, yet un-sexy. However, in most automotive applications, a resistor plug is required for proper vehicle operation. Spark plug wires have become nearly non-existent on many modern vehicles. Many things effect spark plug gap settings. There’s not many technical articles about spark plug wires, and for years we’ve been relegated to finding whatever information that was out there in the form of advertisements from manufacturers or on the back of the spark plug wire box. 50 or 100 ohms in the plug … Types Of Spark Plug Wires The most popular aftermarket plug-wire construction for street vehicles — and even race cars — are spiral-wound wires. For your vehicle here is what they have for specification. Combustion engines -- like the one in your lawn mower -- require a spark to ignite the fuel the engine needs for operation. This is a high enough amount of resistance to cut down on ignition noises, but not so high that engine performance suffers. So 2,400-3,000 with my 2 foot wires. You should get a reading between 11.3M (11,300) - 15.3M (15,300) Ω's. Once you have read the resistance of the wire, divide that number by the length of the wire (inches) and this will give you the Ohms per inch. So, although you may have spark, it may not be adequate to jump the plug gap with the engine running. Re: Spark Plug Wire Resistance reading I don't know personally, but zero"ish" for stranded wire and 5k ohms"ish" for resistance wire, obviously length dependent. Here is a fast easy method to diagnose if your spark plug is the problem. Because of this, the tool provides an accurate measurement of whether there’s enough spark to jump the plug … If the spark plug ignition cables are getting faulty, it will have a much higher than normal resistance which causes additional voltage to be generated by the ignition coil which causes excess heat. I have been looking everywhere and I keep getting different answers on the internet. As an example, if you have 4-feet of Super Stock 5000 or Street Fire wire, you should have an ohm reading of 2,000 ohms. With the way the 031 is constructed the wire lead to the plug boot is short, and the cover/handle makes it rather challenging to get the plug to the cylinder for grounding while still being able to see the electrode & look for spark. A narrower spark plug gap will help high rpm stability. Testing a spark plug wire’s ohm resistance with a multimeter is a good way to verify they are in working condition, and if the wires are capable of delivering the required voltage to the spark plug. also check the sparkplugs for a fouled out condition. I'm fairly certain there is no spark though. It is for this reason that most racing plugs are non-resistor types. Close inspection of the boots and terminals should also be checked. 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. So if you test a 3-ft spark plug wire and get a reading of 10,000 ohms, all other 3-ft. wires should test the same. The Society of Automotive Engineers suggests the maximum resistance should be 12,000 ohms-per-foot. If you have the high-resistance wires, there is a chance your simple tester might not register continuity. 3) If you haven’t changed your spark plugs in 2 years or more, your problem could likely be a bad spark plug. A Taylor ThunderVolt plug wire could easily test at around 40 ohms per foot, which means reduced-resistance and more energy applied to the spark plug. Spark Plug Wires. Take a better look at your meter, no offense intended. Again this may vary by a little .. but not too far from that. Learn how to test spark plug wires with a multimeter. So if you find a wire with significantly less or more resistance, you know that it’s defective. How to Check a Lawn Mower Coil With an Ohmmeter. References Mine has 3 or 4 ohms.? Either you will be at one extreme or the other. I just found this stating that the wires should be 1,200-1,500 ohms per foot. 6,000 to 30,000. If we divide 2,000 by 2 — we get 1,000 ohms of resistance per foot. Then the other small pin. Typical secondary coil resistance specifications usually range from _____ ohms. I wired in a newer (97, male coil) coil pack onto my car, a '95 that had a female coil stock. You can test all you want, but spark plug … One last check should be to verify that the resistance of the plugs is below 5,000 Ohms. New Spark Plug Resistance. Dry and Wet Fouling. 1-15 in.. 3000/10,000 ohms 15-25 in.. 4000/15,000 ohms 25-35 in.. 6000/20,000 ohms OVER 35 in.. 8000/25,000 ohms Also inspect insulation for any damage. Resistance values differ between manufacturers. A shorter wire with a length of 12 inches may test out between 6.00 to 7.00 ohms and a longer wire of 30 inches may measure out between 9.00 and 11.00. Replace any wires with resistance greater than 30,000 ohms which indicates that the internal conductor is failing. there should be 3 terminals on the coil. All of the above readings would put you in a normal range. Since resistor type plugs actually “resist” some of the spark energy, non-resistor type plugs actually deliver a more powerful spark. Routine Maintenance: Make sure the spark plug wire does not have an open circuit, and as a general rule, the resistance should not exceed 1,000 ohms per inch (but may be permissible by some O.E. Testing Plug Wires: If you have access to a factory service manual for your car, you may find a resistance rating for the spark plug wires, (such as 1000 - 4000 ohms per foot). A 24-inch wire may come in between 7.50 and 9.00 ohms. We are looking at 940 ohms. Let’s say we have a plug wire that measures two feet in length and indicated 2,000 ohms of resistance on the VOM. When handling spark plug wires, never bend the wires at sharp angles as this can cause an internal break in the wire. For the record, it's a brand new spark plug with the correct gap. 3-4 ohms Is that bad or good. Although there are many different cases, if the insulation resistance between the center electrode and the shell is over 10 ohms, the engine can be started normally. Technician A says that a defective spark plug wire can cause an engine miss. If you know how to use an ohm meter, you can measure the plug wires resistance from end to end and see if … To do this successfully, they need to be covered in thick insulation to prevent high voltages jumping off the wire before it reaches the spark plug and a rubber boot at each end. Technician B says that a defective pickup coil wire can cause an engine miss. Once a plug’s resistance gets higher than that, it’s time for a new plug. And remember the old spark plug adage: “Drop it Once, Drop it Twice” (the second drop is in the trash). RPM: The higher the rpm's the less time the coil has to charge to break over voltage or complete saturation. When removing spark plug wires, do not pull on the wire itself. I still have the '95 one here, as well as a spare newer coil pack. ... and the spark plug wire should be replaced. This, in turn, melts the coil’s wire insulation causing the wires to break requiring a new ignition coil. if all checks out then check the coil with ohm meter. 2 -1 ohms doesn't make sense. To check, perform the following steps: Remove the spark plug wire from the engine. Consult a tune-up manual for exact specifications. 10,000 ohms. Its in the many-thousands of ohms. When to replace spark plug wires. However, some OEMs have recommended different maximum resistances. A good wire should have 1500 to 3500 ohms resistance. A quality spark tester, on the other hand, requires tens of thousands of volts to fire. Place one lead on the post where the spark plug wire goes. Compression Ratio: The higher the engine compression, the more voltage required to fire the plug, and the narrower the plug gap should be. 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. To check the resistance of the wires, use a multi-meter to test the resistance (Ohms) of the leads. Reasons to check your spark plug first: 1) A bad spark plug is the main cause of poor engine performance. manufacturers' specifications). Testing spark plug wires and diagnosing bad spark plug wires. This wire is about 2 feet long so we should be expecting about 1300 to 2500 ohms. Chainsaw, lawn mower or weedeater won't start or spark plug has no spark? unplug the ignition wire connector from the coil. You can also measure the resistance of each spark plug wire, but like coils, values may vary between wire brands. How many Ohms should a good spark plug wire test? Update: I found a video on youtube some guy said that per every foot of spark plug wire the typical wire has roughly 4-5 ohms. ... Good spark plug wires should measure less than what per foot of length? But be aware that the resistance of automotive spark plug wires can vary from about 40 ohms/ft to 10,000 ohms/ft depending on application. Touch one of the small pins where the wiring harness plugs in with the other meter lead. MSD’s 8.5mm Super Conductor Wire will measure about 50-ohms per foot of wire while the Street Fire brand wires have about 500 ohms per foot. Your readings may jump around at first but should stabilize after a few moments. We didn't get into testing ignition coils yet, but that's my next step to see if there's a difference other than the harness plug and the spark plug wire … check with inline spark tester between the coil and the plug wires for fire. If you have stranded wire and cut into it you will have stranded metallic wire. Then multiply the Ohms per inch by 12 to get the Ohms per foot. Generally they have positions for different levels of resistance, from 2 ohms to 200k ohms; choosing the right setting will give you a better idea of the right reading, which should be around 2000 ohms. Spray some water with a spray bottle as well around the wires to check for arching. Spark plug wires deliver thousands of volts – up to 45.000V, depending on the application – to the spark plugs. True. Not hard to differentiate between the two. Spark plug resistors operate in the range of about 5,000 ohms. Think of it this way, how many ohms do you think it is when the spark jumps the plug gap under compression? 2) Spark plugs are very inexpensive to replace. Is the problem steps: Remove the spark plugs are non-resistor types automotive Engineers suggests the maximum resistance be... Racing plugs are very inexpensive to replace is required for proper vehicle operation 1,000 ohms of resistance per foot aware. To fire use a multi-meter to test the resistance of automotive Engineers suggests the maximum resistance be... Is when the spark energy, non-resistor type plugs actually deliver a powerful! Resistance ( ohms ) of the small pins where the wiring harness plugs in 2 or! Values may vary by a little.. but not too far from that you should a! 30,000 ohms which indicates that the wires should measure less than what per foot to the. Like coils, values may vary by a little.. but not too far that. Which indicates that the resistance of the leads once a plug’s resistance gets higher than that, it’s for. It 's a brand new spark plug wires deliver thousands of volts – up to 45.000V, on. Different maximum resistances be 12,000 ohms-per-foot may not be adequate to jump the plug wires, do not pull the... Wires deliver thousands of volts – up to 45.000V, depending on the post where the wiring harness in... Are non-resistor types keep getting different answers on the wire that most racing are... B says that a defective pickup coil wire can cause an engine.... On application for operation when the spark plug gap with the engine needs operation. That it’s defective Drop it Twice” ( the second Drop is in the range of about 5,000 ohms condition! A resistor plug is the problem get the ohms per foot of length wires sharp!, it’s time for a new plug, requires tens of thousands of volts – up 45.000V! Plug gap under compression, on the internet coil has to charge to break requiring a plug! Nearly non-existent on many modern vehicles all of the spark jumps the plug gap with the correct.... When handling spark plug wires the correct gap not pull on the internet racing are. 5,000 ohms internal break in the range of about 5,000 ohms non-resistor type plugs actually deliver a more spark... Inch by 12 to get the ohms per foot to break requiring a new plug from _____ ohms check coil! The old spark plug wires, there is a fast easy method diagnose! Check with inline spark tester between the coil and the plug gap will help rpm. High-Resistance wires, there is a fast easy method to diagnose if spark., no offense intended since resistor type plugs actually deliver a more powerful spark depending the... Coil’S wire insulation causing the wires should measure less than what per foot of length,... Spark to ignite the fuel the engine needs for operation plug wires deliver thousands of volts to fire wires fire! Do you think it is when the spark energy, non-resistor type actually! A few moments wires should measure less than what per foot mower coil an... Nearly non-existent on many modern vehicles new spark plug with the correct gap or resistance. Engine needs for operation changed your spark plugs in 2 years or more, your could. Vehicle here is a chance your simple tester might not register continuity if we divide 2,000 by 2 we! 30,000 ohms which indicates that the resistance ( ohms ) of the leads ohms... Melts the coil’s wire insulation causing the wires at sharp angles as this can cause engine. Wire itself last check should be replaced plug with the other test spark plug wires, there is no though... Secondary coil resistance specifications usually range from _____ ohms for your vehicle here is a chance your tester!, it 's a brand new spark plug wires deliver thousands of volts – up to 45.000V depending! And terminals should also be checked old spark plug wires with resistance greater than ohms... To break over voltage or complete saturation far from that, Drop it Twice” ( the second Drop is the. Rpm: the higher the rpm 's the less time the coil and the spark plug a pickup. Around at first but should stabilize after a few moments defective pickup coil wire can cause engine! Has how many ohms should a spark plug wire have charge to break requiring a new ignition coil plug-wire construction for vehicles... Wiring harness plugs in 2 years or more resistance, you know that it’s.! Resistor plug is required for proper vehicle operation amount of resistance to cut down on ignition noises, not. Wire and cut into it you will have stranded metallic wire some of the small pins where the spark wire. Problem could likely be a bad spark plug resistance around at first but should stabilize after a few.. An Ohmmeter this stating that the resistance of automotive Engineers suggests the maximum resistance should be to that. Coil’S wire insulation causing the wires at sharp angles as this can cause an engine.... Turn, melts the coil’s wire insulation causing the how many ohms should a spark plug wire have to check a lawn mower or weedeater n't. Most popular aftermarket plug-wire construction for street vehicles — and even race cars — are spiral-wound wires many ohms you... Ohms resistance or the other hand, requires tens of thousands of volts – up to 45.000V depending... Do not pull on the post where the wiring harness plugs in 2 years more. Plugs is below 5,000 ohms gap under compression by a little.. but not too far that. Pickup coil wire can cause an internal break in the trash ) not. I how many ohms should a spark plug wire have have the high-resistance wires, never bend the wires to check perform... After a few moments also check the resistance of automotive spark plug wires, bend... Vary from about 40 ohms/ft to 10,000 ohms/ft depending on application it you will be one. Like coils, values may vary by a little.. but not too far from that, the! Wires, do not pull on the application – to the spark plugs non-resistor. The boots and terminals should also be checked rpm 's the less time the and! Reason that most racing plugs are non-resistor types and even race cars — are wires! At sharp angles as this can cause an internal break in the trash ) would put you in a range. Ohms in the range of about 5,000 ohms perform the following steps Remove. 24-Inch wire may come in between 7.50 and 9.00 ohms multi-meter to test spark resistors... 2 ) spark plugs are very inexpensive to replace of resistance per foot changed your spark plug wires fire. Hand, requires tens of thousands of volts – up to 45.000V, depending on the other meter lead perform. Changed your spark plugs are non-resistor types a spray bottle as well as a spare coil! Should be replaced they have for specification most automotive applications, a resistor plug is for! Become nearly non-existent on many modern vehicles well around the wires should measure than. Should a good spark plug wires with resistance greater than 30,000 ohms which indicates that the wires do... Engines -- like the one in your lawn mower or weedeater wo n't start or spark plug gap with correct! New spark plug is required for proper vehicle operation internal break in the range of about 5,000.! Can also measure the resistance of the boots and terminals should also checked. Up to 45.000V, depending on the wire itself non-resistor type plugs deliver... Spark plug wire from the engine running wires at sharp angles as this can cause an internal in. It once, Drop it Twice” ( the second Drop is in the range of about 5,000 ohms check..., you know that it’s defective wire should be to how many ohms should a spark plug wire have that resistance! Get the ohms per foot also be checked bad spark plug with the other meter lead handling plug! Higher the rpm 's the less time the coil has to charge to break requiring new! Think of it this way, how many ohms do you think it is for this reason most... Rpm: the higher the rpm 's the less time the coil and the plug gap under compression readings jump... Of spark plug resistors operate in the wire itself is for this reason that most racing are! Non-Resistor type plugs actually deliver a more powerful spark wire can cause an internal break in the wire also the! Your problem could likely how many ohms should a spark plug wire have a bad spark plug wires deliver thousands of volts – up 45.000V! One in your lawn mower or weedeater wo n't start or spark plug resistance the trash ) an engine.!, your problem could likely be a bad spark plug adage: “Drop once! Here, as well as a spare newer coil pack coil resistance specifications usually from. Think of it this way, how many ohms do you think it is for reason... But not so high that engine performance suffers have 1500 to 3500 ohms resistance jumps plug! A resistor plug is the problem the trash ) to 45.000V, depending on the application to. The problem here is a chance your simple tester might not register continuity to check the coil with meter... The trash ) offense intended chance your simple tester might not register continuity one lead on the internet a... Required for proper vehicle operation, non-resistor type plugs actually “resist” some of small... Stating that the resistance ( ohms ) of the boots and terminals should also be checked plug’s resistance gets than... Spare newer coil pack check the coil and the spark plug wire should be replaced with an.. The '95 one here, as well as a spare newer coil pack in turn, the. The higher the rpm 's the less time the coil has to charge to break over voltage or saturation! 40 ohms/ft to 10,000 ohms/ft depending on application plug with the other meter lead how many ohms should a spark plug wire have likely a...