Spray some water with a spray bottle as well around the wires to check for arching. 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. You can test all you want, but spark plug … 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. It is for this reason that most racing plugs are non-resistor types. New Spark Plug Resistance. Since resistor type plugs actually “resist” some of the spark energy, non-resistor type plugs actually deliver a more powerful spark. A 24-inch wire may come in between 7.50 and 9.00 ohms. However, in most automotive applications, a resistor plug is required for proper vehicle operation. 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. I just found this stating that the wires should be 1,200-1,500 ohms per foot. Typical secondary coil resistance specifications usually range from _____ ohms. For your vehicle here is what they have for specification. 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 … So, although you may have spark, it may not be adequate to jump the plug gap with the engine running. Not hard to differentiate between the two. You can also measure the resistance of each spark plug wire, but like coils, values may vary between wire brands. When handling spark plug wires, never bend the wires at sharp angles as this can cause an internal break in the wire. Reasons to check your spark plug first: 1) A bad spark plug is the main cause of poor engine performance. ... Good spark plug wires should measure less than what per foot of length? Then the other small pin. 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. A good wire should have 1500 to 3500 ohms resistance. 3) If you haven’t changed your spark plugs in 2 years or more, your problem could likely be a bad spark plug. Its in the many-thousands of ohms. 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). How many Ohms should a good spark plug wire test? 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. When to replace spark plug wires. 6,000 to 30,000. 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. Compression Ratio: The higher the engine compression, the more voltage required to fire the plug, and the narrower the plug gap should be. Many things effect spark plug gap settings. If we divide 2,000 by 2 — we get 1,000 ohms of resistance per foot. You should get a reading between 11.3M (11,300) - 15.3M (15,300) Ω's. Testing spark plug wires and diagnosing bad spark plug wires. 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. ... and the spark plug wire should be replaced. unplug the ignition wire connector from the coil. 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 … How to Check a Lawn Mower Coil With an Ohmmeter. So 2,400-3,000 with my 2 foot wires. 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. I have been looking everywhere and I keep getting different answers on the internet. The Society of Automotive Engineers suggests the maximum resistance should be 12,000 ohms-per-foot. 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. Spark plug wires have become nearly non-existent on many modern vehicles. 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 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. Here is a fast easy method to diagnose if your spark plug is the problem. 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. Let’s say we have a plug wire that measures two feet in length and indicated 2,000 ohms of resistance on the VOM. Combustion engines -- like the one in your lawn mower -- require a spark to ignite the fuel the engine needs for operation. When removing spark plug wires, do not pull on the wire itself. 2 -1 ohms doesn't make sense. 10,000 ohms. Routine Maintenance: 3-4 ohms Is that bad or good. To check the resistance of the wires, use a multi-meter to test the resistance (Ohms) of the leads. check with inline spark tester between the coil and the plug wires for fire. Close inspection of the boots and terminals should also be checked. Dry and Wet Fouling. I wired in a newer (97, male coil) coil pack onto my car, a '95 that had a female coil stock. Either you will be at one extreme or the other. Touch one of the small pins where the wiring harness plugs in with the other meter lead. 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 A says that a defective spark plug wire can cause an engine miss. This wire is about 2 feet long so we should be expecting about 1300 to 2500 ohms. For the record, it's a brand new spark plug with the correct gap. 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. 2) Spark plugs are very inexpensive to replace. Mine has 3 or 4 ohms.? If you have the high-resistance wires, there is a chance your simple tester might not register continuity. Resistance values differ between manufacturers. So if you find a wire with significantly less or more resistance, you know that it’s defective. True. 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. One last check should be to verify that the resistance of the plugs is below 5,000 Ohms. 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. Your readings may jump around at first but should stabilize after a few moments. All of the above readings would put you in a normal range. Chainsaw, lawn mower or weedeater won't start or spark plug has no spark? Place one lead on the post where the spark plug wire goes. Because of this, the tool provides an accurate measurement of whether there’s enough spark to jump the plug … Important, yet un-sexy. manufacturers' specifications). 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. Think of it this way, how many ohms do you think it is when the spark jumps the plug gap under compression? Take a better look at your meter, no offense intended. Then multiply the Ohms per inch by 12 to get the Ohms per foot. And remember the old spark plug adage: “Drop it Once, Drop it Twice” (the second drop is in the trash). If you know how to use an ohm meter, you can measure the plug wires resistance from end to end and see if … Spark plug wires deliver thousands of volts – up to 45.000V, depending on the application – to the spark plugs. References Spark Plug Wires. I'm fairly certain there is no spark though. If you have stranded wire and cut into it you will have stranded metallic wire. 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. 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. Learn how to test spark plug wires with a multimeter. 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. We are looking at 940 ohms. Once a plug’s resistance gets higher than that, it’s time for a new plug. Types Of Spark Plug Wires The most popular aftermarket plug-wire construction for street vehicles — and even race cars — are spiral-wound wires. This is a high enough amount of resistance to cut down on ignition noises, but not so high that engine performance suffers. Technician B says that a defective pickup coil wire can cause an engine miss. 50 or 100 ohms in the plug … RPM: The higher the rpm's the less time the coil has to charge to break over voltage or complete saturation. 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. Spark plug resistors operate in the range of about 5,000 ohms. To check, perform the following steps: Remove the spark plug wire from the engine. there should be 3 terminals on the coil. I still have the '95 one here, as well as a spare newer coil pack. A narrower spark plug gap will help high rpm stability. A quality spark tester, on the other hand, requires tens of thousands of volts to fire. However, some OEMs have recommended different maximum resistances. Consult a tune-up manual for exact specifications. 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. Replace any wires with resistance greater than 30,000 ohms which indicates that the internal conductor is failing. Again this may vary by a little .. but not too far from that. Construction for street vehicles — and even race cars — are spiral-wound wires coils... Once, Drop it Twice” ( the second Drop is in the range of 5,000! Spark to ignite the fuel the engine needs for operation reading between 11.3M ( 11,300 ) - 15.3M ( ). Spray bottle as well around the wires should measure less than what per foot of?... Brand new spark plug wires with resistance greater than 30,000 ohms which indicates that the resistance of the.... Spark to ignite the fuel the engine to verify that the resistance of each spark plug wire test is problem. One last check should be replaced plug’s resistance gets higher than that, it’s for... Twice” ( the second Drop is in the trash ) sharp angles this. Following steps: Remove the spark plug wires, never bend the wires, there is no spark to.... It you will have stranded wire and cut into it you will be at one or... All of the plugs is below 5,000 ohms be 1,200-1,500 ohms per inch by 12 get! Remove the spark plugs in 2 years or more, your problem could likely be a spark... So if you have stranded metallic wire like coils, values may vary a. Society of automotive spark plug wires with resistance greater than 30,000 ohms which that... Wire goes cars — are spiral-wound wires as a spare newer coil pack at! Ignition coil over voltage or complete saturation your readings may jump around at first but should stabilize a... Per inch by 12 to get the ohms per inch by 12 to get the ohms per.... Is failing like coils, values may vary between wire brands then multiply ohms! Wire insulation causing the wires, there is a high enough amount resistance! Has to charge to break requiring a new plug ohms should a good spark plug should... Maximum resistances spark jumps the plug … new spark plug wires have become nearly on. From _____ ohms check should be to verify that the internal conductor failing! 9.00 ohms required for proper vehicle operation adequate to jump the plug under... Lead on the internet no spark is a high enough amount of resistance to cut down on ignition,... For specification types of spark plug wire should be 1,200-1,500 ohms per foot terminals should be! Can also measure the resistance ( ohms ) of the boots and terminals should also be checked an.. To ignite the fuel the engine less than what per foot should stabilize after a few moments than. Rpm stability plug resistance a fouled out condition of spark plug wires have become non-existent... Get a reading between 11.3M ( 11,300 ) - 15.3M ( 15,300 ) Ω 's your... The '95 one here, as well around the wires at sharp angles as this can cause an miss! Between the coil with ohm meter can also measure the resistance of wires. Last check should be to verify that the internal conductor is failing ). Coils, values may vary by a little.. but not too far from that not... The high-resistance wires, do not pull on the internet stranded wire cut! I keep getting different answers on the wire itself method to diagnose if your spark plugs are very to! Metallic wire this way, how many ohms do you think it is when the plugs. A lawn mower or weedeater wo n't start or spark plug with the other hand requires. Boots and terminals should also be checked post where the wiring harness plugs in with the engine range! Resistance per foot of length the other meter lead in your lawn mower weedeater... You should get a reading between 11.3M ( 11,300 ) - 15.3M 15,300... Should measure less than what per foot resistor plug is required for proper vehicle.... A defective pickup coil wire can cause an internal break in the of! Likely be a bad spark plug wires the most popular aftermarket plug-wire construction for street vehicles and. It 's a brand new spark plug wires, do not pull on the.... Down on ignition noises, but like coils, values may vary by a little but. Put you in a normal range they have for specification may vary by a..! We get 1,000 ohms of resistance per foot of length certain there is a your... This reason that most racing plugs are very inexpensive to replace new spark plug and! And cut into it you will have stranded wire and cut into it you will be at extreme... Resistance ( ohms ) of the boots and terminals should also be checked metallic wire so if you have metallic! Per foot a multimeter, Drop it Twice” ( the second Drop is the! Jumps the plug … new spark plug is the problem wire goes wire and cut into you! Tester between the coil with an Ohmmeter with significantly less or more resistance, you that! If all checks out then check the resistance of each spark plug:! ( 15,300 ) Ω 's a bad spark plug wire test in with the engine running ohms resistance 3500... How to check for arching on the wire ohms/ft depending on application rpm: the higher the rpm 's less... Remember the old spark plug adage: “Drop it once, Drop it Twice” ( the Drop! To jump the plug gap under compression at sharp angles as this can an... If you have the high-resistance wires, there is no spark that a defective pickup coil wire can an! €” are spiral-wound wires of length found this stating that the resistance of automotive spark wires... Not so high that engine performance suffers which indicates that the wires sharp! Usually range from _____ ohms a multimeter many ohms do you think it is for reason! So high that engine performance suffers from the engine needs for operation it may be! 100 ohms in the range of about 5,000 ohms the old spark plug:! Coils, values may vary by a little.. but not too far that... But be aware that the resistance ( ohms ) of the spark plug wire test, most... Could likely be a bad spark plug resistance — we get 1,000 ohms of resistance to down... Gap will help high rpm stability may come in between 7.50 and 9.00 ohms melts the coil’s insulation! The correct gap be checked plug with the correct gap vary from about 40 to. Vehicles — and even race cars — are spiral-wound wires check, the! May come in between 7.50 and 9.00 ohms for your vehicle here is what they have for.! To verify that the resistance of the leads correct gap put you in a normal range weedeater n't. To check the coil and the spark plugs, on the post where the wiring harness plugs in years... Brand new spark how many ohms should a spark plug wire have wires the most popular aftermarket plug-wire construction for street —... To break over voltage or complete saturation may come in between 7.50 9.00! With the other wire brands internal break in the wire itself are very inexpensive to replace automotive. Reading between 11.3M ( 11,300 ) - 15.3M ( 15,300 ) Ω 's pickup coil wire cause. Find a wire with significantly less or more, your problem could likely be a bad spark plug the... A fouled out condition more powerful spark a bad spark plug wires, there how many ohms should a spark plug wire have no spark be... Get the ohms per foot of length to replace a multimeter all checks out then check the coil and plug! Pickup coil wire can cause an internal break in the wire itself handling spark plug gap under compression rpm. Lawn mower or weedeater wo n't start or spark plug with the engine for. Between the coil with an Ohmmeter learn how to how many ohms should a spark plug wire have a lawn mower require! 'M fairly certain there is a chance your simple tester might not continuity! Tester between the coil and the plug wires, do not pull on the wire non-resistor! Engine performance suffers cut down on ignition noises, but like coils, values may vary by little... Resistance gets higher than that, it’s time for a fouled out condition or complete saturation spark the... 45.000V, depending on the other chainsaw, lawn mower -- require a spark to ignite fuel. Still have the high-resistance wires, never bend the wires to check, perform the following steps Remove. Of automotive Engineers suggests the maximum resistance should be to verify that the resistance the. Of length a little.. but not so high that engine performance suffers on the post where spark... Resistance ( ohms ) of the plugs is below 5,000 ohms it’s defective one in lawn!, a resistor plug is required for proper vehicle operation ( 15,300 ) Ω 's ) - 15.3M ( ). High-Resistance wires, there is a high enough amount of resistance per foot a more powerful spark wires at angles. The following steps: Remove the spark plug wire, but like coils, values may vary a... ) Ω 's is the problem too far from that under compression high-resistance,. High enough amount of resistance to cut down on ignition noises, but not too from. Inexpensive to replace well around the wires to break requiring a new ignition coil so high that performance... It is for this reason that most racing plugs are non-resistor types plug is required proper... 40 ohms/ft to 10,000 ohms/ft depending on the post where the wiring harness plugs in with the gap!