Briggs and Stratton Ignition Coil Testing

Learn How To Test A Briggs & Stratton Ignition Coil

Tools/Parts Required 

  • Multi-Meter

Step 1.

Set the multi-meter to the 20 k ohms setting. A working ignition coil will give a reading of between 2.5 – 5 k ohms.

Step 2

Set the positive lead of the multi-meter in position where the spark plug would usually insert – ensure it has made good contact. Place the negative lead onto the metal body of the ignition coil – again ensuring it makes proper contact.

Step 3

Look for the reading on the multi-meter. A reading of 2.5-5.0 Kohms indicates the ignition coil is in working order. No reading indicates a broken circuit, as reading get higher the spark will weaken until it is no longer present.

 


95 Comments

  1. I’m confused. You set the meter on the 25 ohm range to measure 2,500 to 5,000 ohms, and then say that the coil should be between 2.5 and 5.0 ohms. Do you mean set the meter on the 25 kohm range, and the coil should be between 2.5 and 5.0 kohm (1 kohm=1,000 ohms)? That is more the range I would expect. Also, what if any reading would you expect on the kill wire that comes out of the coil? My coil reads 10 kohms but more significantly the kill wire is 0 ohms to frame, which I suspect means it is FAB. Thanks for posting this anyway – makes life easier. 🙂

    • Hi

      Sorry to confuse you the write up had a few errors we had not noticed. You are correct the Multimeter is set to 20 Kohms and the Reading for a working coil should be between 2500-5000 Ohms. The Kill wire should read 0 ohms to the frame and between 2500-5000 between the ignition lead.

      • Hi,

        You say here that the kill wire should read 0 ohms to the frame. I thought the kill wire was only grounded to the frame when the switch was in the stop position? I thought it would usually be infinite to the frame?

        Could you clarify?

        thanks

        • Hi

          The kill circuit should have infinite resistance unless it is connected to the frame. Once you connect it to the frame with your multimeter leads it will read 0 resistance.

          • Hello – sorry I’m still a bit confused with the last answer. My B&S engine has just stopped working and I’ve checked the coil and I get about 2,6kohms between the body of the coil and the HT lead connector. But, I get 0 ohms between the stop-switch connection and the coil body – which surprised me as I thought that that was the connection made by the stop-switch (ie it grounded the coil to stop the engine) – can you clarify that one again?

          • Hi

            that reading is okay you should get 0 Ohms from the body of the coil to the stop switch connection. The stop switch should have no continuity when in the open position and continuity in the closed position.

    • My coil has a resistor spark plug cap on the plug wire. From the coil to spark plug connector I’m getting 10.9 thousand ohms. If I take the resistor cap off, I’m getting
      5.8 on the coil to end of plug wire and 5.1 on the resistor plug cap. Is that 10.9 too high.

    • If the reading you are getting is within the required range i would suspect the coil is okay. However i can’t be sure as i haven’t tested those particular coils before.

  4. Hi, the kill wire should be around haalf ohm when the killswitch is not grounded. It’s an inductance shunt. If you read open, it will keep running through the brake.

    • Hi

      This will not determine if the coil is failing when hot, You could put your coil in the oven at around 60 Degrees for a short time then test it at that temperature to determine if anything has changed

    • Yes a higher reading means there is more resistance to electrity flow so the spark would be weaker as you get closer to 5K Ohms

    • Yes if you are experiencing problems relating to lack of or weak spark a reading above 5 k ohms indicates your coil is in need of replacement

    • Hi

      a lower reading can indicate one of the windings in the coil has shorted causing less internal resistance, This would also cause failure of the coil.

    • Hi

      Briggs and stratton only provide a range of between 2.5 and 5 K ohms as a working range for the coils.

  10. You say you have the new cool for sale on the website but I’m not finding it when I search for coils have a link? I need a coil for an old outboard and it looks to be the same unit where it slides over the stacked plates and one is bent up to hold it.

  11. I have a B&S 5hp outboard motor (model AA0101) which doesn’t start. It is getting fuel (somewhat). I have cleaned the carb. It is getting very little if any spark. I took off the coil. I measured between the kill switch and the body and it says 0 ohms. Between the body and the HV it reads 6.5kohms. Between the kill switch and the HV it also reads 6.5kohms. I need my motor to get by boat out of the harbor, so what can I do to get it started if, indeed, it is the coil? Thanks

    • If the spark is weak it will be very hard to start and run your outboard, You may have a slim chance with some engine starting spray. The best option is the replace the coil and restore the spark.

      • I replaced the ignition coil with a brand new one from ereplacement parts and did a reading on the new one. The reading was the same as the old one, so either I’m not reading it correctly, or the new one is bad as well. It’s getting gas (I checked the carb bowl) and compression, but still no spark. Is there a way to check if the kill switch wires are bad, or if it will start or give spark by bypassing the kill switch? They don’t seem to be frayed or touching anything. I don’t know what else to do.

        • It is unlikely that the new coil is also bad it may just be an incorrect reading, Or the coil readings are different for outboard engines.

          If you have not tried a new spark plug I would try that first, Otherwise you will need to check for continuity in all the wires & test or replace any other components in the ignition system until you find the problem.

          You can remove or disconnect the kill switch to test if it is the problem.

  12. I was initially getting a reading of 9k ohms from my original coil. I recently purchase a new coil and got around the same reading. Could there be an issue with the spark plug boot cover as I haven’t replaced this. I have replaced the spark plug.

    • There could be an issue within the connect from the cover to the spark plug, This is however not very common

  13. Hey everyone. I was kind of surfing this site and read all kinds of ways to test Magneto’s or electronic ignitions. I have been servicing mowers for many years, including the old breaker points ignition systems, and the easiest way I have found to test these things is by the idea of “seat of your pants technique.”
    What I propose is “not” the recommended way but, in my opinion, the quickest was to test these things. If you can stand a little shock, then here it goes.
    I first remove the boot over the spark plug then remove spark plug. This will do two things. One it will eliminate the possibility of engine accidentally starting and eliminating any compression in combustion chamber. Here is the shocking part. If your plug wire has a boot covering the connector then insert one of you fingers into the boot ant then put another finger of same hand anywhere on the block. Pull starter rope or turn on starter enough to briefly turn flywheel. You should get a decent shock, but not enough to harm you.
    If your wire does not have the boot, consider yourself somewhat lucky. Just hold the wire “close” to the block and look for a spark jumping from wire to block. May need to be in a relatively dark place to see spark

    This procedure is assuming you have pulled break release / kill handle back to the run position. If no shock, check kill switch which will, unfortunately, means removing top of engine cover.

    If you do get shock. Then ignition is good. Look elsewhere for other problems.

    • What you are saying might sound stupid but the fact is that this is about the best way to find out if anything is happening from the coil or not, especially when the spark is weak, or can’t be seen due to lighting problems, or when the wires can’t be properly secured/grounded to do the test.

      Thumbs up (grounded or not)!

  14. Hello i have an auto ranging multi meter so i cant set it to 20k but i assume its accurate as when i test my coil it reads 7.5k so my coil is bad?

    • Hi

      A reading of 7.5k is high and would suggest your spark is much weaker then it would be with a lower in spec reading.

  15. OK, all the resistances check out properly but I still get no spark. What next? I assume my 5 HP B &S engine must have a capacitor some where. Does this mean I have to pull the flywheel?
    Also, the 2.5-5 Kohm resistance is for one winding. What about the other? Is there a way to check its resistance?

    • Hi Howard

      This test is testing both winding’s in series, I do not know of a way to test one winding at a time at the moment. If you have not replaced the spark plug that would be the first thing. There is no capacitor unless you have a points ignition system. If you cannot get spark with a new plug & the kill switch wire is not earthed then the nest step is to replace the coil.

  16. I have a Briggs and Stratton 4.5 hp mower. No spark. Old coil read approx 4.9 ohms using analog multimeter. Ordered new coil. New coil reads 6.0 ohms right out of the box. Is this too high? Also, I noted that the curvature of the coil is not the same as the shape of the flywheel. In other words. the gap between the coil and the flywheel is not consistent as the two surfaces are not parallel to each other. Is this also a problem? Wish I could explain it better.

    • 6 ohms may not be too high as the coil could be different to the original coil and may use different specs, It seems like the coil may not be the correct fit if the curvature does not line up correctly, It is best for it to be consistent and about the width of a business card for the air gap, You should try the coil anyway it may work if it has been sold to you as a replacement.

  17. My Briggs lawnmower has a resistor in the spark plug cap and a metal cover on the cap. Do the same ohm meter readings apply? I get no reading after the resistor. 4.5K before the resistor.

    • Hi Bob

      The resistor would change the reading, However if you get no reading after the resistor it would suggest the resistor is damaged.

  18. Thanks so much for your fast reply. I plan to remove the resistor from the spark plug cap (and the steel cover) and use a resistor spark plug. This should work?? I have seen a few Briggs magnetrons and they appear to be similar except for this one with the resistor and steel cover. Is this style unusual or discontinued. Thanks again for your help.
    Regards,
    Bob Brown.

    • Yes a resistor spark plug should work fine as a replacement, I have not seen one with a resistor so I suspect they are not very common

  19. The Briggs spark plug cap with the internal resistor seems to be obsolete and replaced. I have two old lawnmowers with this setup. Both mowers resistors failed. No ohm reading downstream of the resistor. I removed the resistors and all is good. Google will show this and one from NGK.
    Regards from Canada.

  20. Have had similar experience with a Briggs engine on a Craftsman mower..with kill wire removed from mower,
    1. No spark
    2. New plug
    3. Replaced coil…. new reads 6200 ohms..old reads 4800 ohms.
    4. Checked another identical new coil at dealer…reads 6000 ohms.
    5. Flywheel key checked…..ok…..wheel may be 1/16″ displaced, no more….STILL NO SPARK..magnets seem strong…..Tested with screwdriver tip.
    6. Will check will local lawnmower repair shop for used coil and compare resistance readings

    Any help to get mower running……carb has had overhaul kit installed.

    • Hi Mel

      It sounds like you have replaced most of the important parts, Coils over 5kohms may well work as the 2.5-5Kohm range is suggested for older models similar to the mower in the video, newer or different models often can have different specs. If the magnets are strong and the coil and spark plug is new then the most likely issue is incorrect too large air gap or incorrect wiring causing the coil not to work properly.

  21. Hi, I have a question. If I am getting spark in a spark tester, but getting continuity with the kill switch in both on and off positions, is that still an ignition coil issue, or fuel related? (compression test was good). This is a Craftsman Snowblower. Thank you!

    • Hi

      Usually in one position the off switch will ground the coil causing the spark to stop, Depending on where you are measuring you can have continuity with the switch both in the on and off positions. If you have a spark you should try putting a few drops of fuel in the spark plug hole. If the blower starts briefly it is likely to be a fuel issue. If it does not start compression may be low.

      • If the kill wire connector coming off the coil going to the primary coil is suppose to kill the engine – only when the kill wire is grounded to the engine – how can it have continuity at all times?”?? Shouldn’t matter where you measure. Remove the kill wire from the ignition coil and measure ohms from connect tab on the coil to the frame of the coil… seems if there is not sufficient resistance, the coil is grounded all the time and will not work. Is this right?

        • Hi

          The kill wire should only have continuity when connected to the engine, If you remove the coil and the kill wire then as you said it there should be no continuity between the kill wire connector and the frame of the ignition coil. If there is continuity between the connector and the ignition coil frame there will be no spark as the coil will be grounded.

  22. what should the voltage be at the spark plug when using a voltage meter to check the ignition coil output on most small engines, ie. chain saw while pulling the starter rope?

  23. Hi, just posting to say thanks for the comments here as they helped fix my Briggs and Stratton 35 Classic problems. This was my issue;

    Mower is old; 10 years , but dry-stored, not much use each year, new fuel used every year and old drained at end of season. Oil has never been changed, but topped up once (I think). Never had an issue with it and it will usually start first time after a winter’s lay off when I need it again.

    Problem:

    Used it twice this 2017 season, no issues at all, then come to use it for the third time (and just two weeks after the last time) and it simply will not start. Tried all the following;

    -Checked fuel, tank holding sufficient, also seen to “squirt” into carb. when bulb depressed
    -Not fuel locked; removed plug and checked for excess fuel
    -Pulled up and “locked” the safety bar in place with velcro, and tried again, just in case… no improvement
    -Squirted lighter fuel into plug hole, still no response… beginning to expect spark issue
    -Find and disconnect kill switch wire, to rule that out… no change
    -tried three different plugs; original, “known working” and brand new; no change, still nothing at all
    -get wife to try and check for spark by removing plug, but keeping connected to magneto and wife holding bottom of plug to mower body (with insulated pliers) whilst I pulled cord to turn over engine; results inconclusive, but after argument and scuffle subsides (following Police intervention), 99.9% sure no spark is present

    Solution;

    Removed cowling starter cover and using help provided above, removed ignition HT-lead and magneto assembly and used multimeter to check resistance off the mower; reading of 2.74 Kohms seen, so looks good. Noticed that the magneto surfaces that “face” the flywheel magnets were quite “cruddy” with crap like dried grass(?), and so I used a piece of emery paper to clean up the surfaces, including the surface that goes “face down” where it is screwed to the body (basically, anything metal I could get to that was “black” got sanded until it shone a bit brighter).

    I checked the magnets on the flywheel and they were still strong enough to hold a screwdriver, but I noticed a smaller amount of black crud on the flywheel along this edge where the flywheel would pass the magneto, so I cleaned that off too with the same emery paper.

    With that done, I reinstalled the magneto, paying attention to the “cylinder side” / “this side out” lettering on it, and used a piece of thick-ish card as a gauge to set a gap between the flywheel and magneto (as seen on another video online), as I tightened up the bolts.

    I pulled the card free and satisfied myself there was enough of a gap (to start things off at least), and made one last check of the resistance of the magneto “in-situ” this time, and that still showed around 2.75 Kohms.

    I didn’t bother to try and check the spark and just put the plug in to see what would happen. One quick prime push and a pull and the engine spluttered and almost started, so I was pretty sure I’d sorted it.

    With another priming, and a good solid pull, the engine turned over and started immediately. I was grinning for a few moments, and stopped to tap on the Police van glass and attract my wife’s attention, and who was sitting handcuffed inside. I mouthed “look! Working now!” to her, but wasn’t able to catch her vocal reply although it looked like she was making some “F-sound” words as the Police officer restrained her, and I struggled to lip-read her.

    Of course, after a few minutes when I then released the safety bar to stop the mower, although the engine slowed due to the braking effect on the flywheel, the engine didn’t stop… because i’d not reconnected the kill-switch wire… Doh!

    Pausing briefly to glance at my wife, who was now pointing and laughing at me along with the Police Officer too, I had to think for a moment before realising that I could use the insulated pliers to pull off the plug cap and kill the engine like that, which worked fine.

    Disassembled the cowling cover again, re-connected the kill-switch wire, reassembled again, re-fired engine (still good) and checked for kill-switch by releasing safety bar, and this time the engine was killed straight away.

    So, although I can’t really understand exactly why it went from start first time to not starting between the time I stopped it last and put it away, the cause was the magneto either drifting too far from the flywheel (it was still solidly screwed in, so think this is unlikely, but…), or just too gunked up to give a decent contact “gap” to work.

    Cleaning the magneto surfaces and flywheel, and re-seating the magneto seems to have cured the issue at the moment.

    Oh, and wife gets out in 12 months. 😉

    (all the wife and police stuff was just me joking. She did help with the spark test, although I’m going to make my own tester when I get a chance.

    Regards

    James

  24. My Briggs and Stratton 16hp v twin has no spark with a good spark plug and with the multimeter set on 20k ohms the magneto reads 4.82 ohms on each magneto. Do I need New magnetos?

    • Hi Drew
      The correct reading changes depending on the coil type, For your 16hp Briggs it is most likely the reading could be different so we are unable to say if the coils are good or bad.

  25. I have an older 2hp Briggs engine, model 60102, on a lawn edger, which I am trying to get going. Coil reads 2.76kohms.. I have set coil gap at .012″. I get spark showing in the light of a spark tester when I turn over the engine with a cordless drill but when I attach a new Archer A931P plug to the tester or straight onto the coil lead, then there is NO light in the tester or spark at the plug when grounded on engine block.
    Plug gap is .025″ & condenser gap is .020″ & condenser points have been cleaned.
    Can you please give me some direction from here as I am stumped at the moment.
    Cheers from Australia.

    • Hi Lester

      The coil readings in the video are suitable only for that coil type, Although if you coil is producing a spark it is a sign that it is working. It sounds as if you system is setup correctly and should be working, As you do not get spark with the new plug it may be worth trying an additional plug. If that does not work the only other solution is to begin replacing the electrical components with known working parts until the problem is resolved.

  26. I have a Briggs & Stratton lawn mower with a Quantum 675 engine (126T024830B1). Suddenly it died on me a few days ago and I can’t figure out why.
    Initially I thought that gasoline was contaminated, so I had the fuel tank removed and cleaned. I did the same with the carburetor, but to be honest I didn’t find much debris into either of those.
    After this repair the engine would start briefly but stall after a few minutes. Then I’ve checked the bimetal on the exhaust and was working properly.
    I then checked the governor and was properly adjusted as per B&S guidelines.
    Finally decided to check into the ignition system. Armature clearance was correct. The magnetron resistance (from spark plug cap tip to magnetron body) was about 11kOhm! As per B&S specs this should be between 2.5-5kOhm. What worries me though is the fact that upon disconnecting the plug cap from the lead, noticed that the resistance from the lead to the magnetron body was only 7kOhm! The remaining 4kOhm is the resistance of the plug cap.
    Before starting to replace the wrong parts my question is this, should there be any resistance on the plug cap? I’ve read some threads above and seems that new coils have a resistance of 7kOhms lead to body (excluding the cap).

    • Hi Phillip

      We do not know the Ohm requirements for the newer Briggs and Stratton engines, Although from your analysis of the components 4kOhms seems to be an awful lot of resistance for the plug cap, It could indicate damage to the lead & cap connection and may be what is causing your issue. Typically a weak spark can cause a mower to shut off when it gets hot and the resistance of the ignition module increases.

      • Thanks for your prompt response. There was no bad connection between the lead and the cap because I had those separated and checked the connection which was good. Additionally the total resistance (11kOhm) is basically the sum of the partial resistances of the coil and the cap (7 4).
        With your experience, would you say that the cap alone should have almost no resistance?

  27. Briggs & Stratton Classic 35. For the coil I read a value of 2.79. With the kill switch wire disconnected and a new plug yet I get no spark.
    Can the coil be defective even if in range?
    What else should I check?
    Thanks

    • Hi Fran

      Yes the multi-meter test gives a good indication of whether the coil is working or not but it is not 100% accurate. The coil can still be faulty when within range but it much less likely. In your case if you have a new plug and have the kill switch disconnected it would be likely that your coil is the faulty component as there is nothing else to cause the fault

  28. I have a old Briggs and stratton 8hp (193707-0370-01)and have no spark. For the coil I read value 13,75. Should it be between 2,5-5 also for bigger engines?

    • Hi Stan

      The reading will most likely be different for your larger engine. The 2.5-5 reading is only applicable to the coil in the video which is fitted to the smaller briggs and stratton engines.

  29. I have a B&S 10hp on my generator, after reading above , I am confused could the oil level safety switch be bad ? what should the ohm value for it be and is it like a capacitor
    If you disconnect the coil wire from the stop switch the oil level safety switch is out of the circuit correct. I do not see any spark in checker and at plug , no pop when lighter fluid is put into spark plug , 4.85 k ohms reading on coil. I am still going to get a new coil , any suggestions. cleaning magnet and flywheel.

    • Hi Ned

      The coil of your 10hp Briggs and stratton likely has a different reading then the smaller coil filmed in the above video. I am not familiar with the oil level switches so cannot offer any help there.

  30. I have strange problem, just like few other people above…it is 1998 engine, model 10c902, type 20138 E1.
    No spark, good magnets I believe, coil resistance readings are 2.63 K, brand new spark…ground (stop) is not touching anything, separated the wire, tried 2-3 positions coil from wheel, cleaned the wheel…

    I don’t know what to do?
    Will try to get new coil.

  31. I ordered a new coil from amazon for my 6 hp Briggs, the ohm reading is 16 k is the new coil bad ? the old coil is 4 k and it does work.

    • Hi Bob

      The new coil could be different internally. We cannot tell if this reading means its faulty as this test is applicable only to coil model in the video. Other coils often have different readings.

  32. I have a B&S 450 series 148cc engine on a lawnmower. Poor starting. The coil registers 4.69 Ohm, metal spark plug cap reads a similar 4-5 Ohm and I believe has a resistor. When connected the reading between cap and coil is around 9 Ohm. I get a better spark without using the cap. Is 9 Ohm excessive? Would a simple rubber cap be OK or will the engine/ignition be damaged? Thanks, Clive

    • Hi Clive

      You can run the mower with a standard cap to bypass the included resistor in your current cap. However this would likely only be a temporary solution as the problem causing your weak spark will probably get worse of time till the point that it no longer starts even without the resistor.

      • Many thanks, spark plug and coil are new and did all the Ohm checks without the stop switch lead attached to the coil. Coil gap set correctly with B&S card. Flywheel magnets good and have been cleaned. Plug gap 0.6mm. Still can’t understand a poor spark.

        • That’s unusual with new parts the spark should not be weak. You should check that you are not also using a spark plug with a resistor built in. This is usually designated by a R in the part number e.g J19LM OR RJ19LM if so that could explain the weak spark.

  33. I have a Briggs & Stratton Wheelhouse 5500 generator. The generator is practically new – about 2 hours of use. I have not used the generator in 3 years. It started the last time I used it.
    Motor is getting fresh fuel, no wires are frayed or grounded\ and changed the spark plug,
    I removed the ignition coil and it tests 4.89 ohms consistently, which is withing the acceptable range. I do not get a spark.
    Can ignition coils go bad from non-use?

    Thanks for your help.

    • Hi

      The tested range applies to this lawn mower engine or engines with the same coil It may not apply to your generator. It is possible but very unlikely that the ignition coil is faulty. They rarely go bad after so few years. I would investigate the Off/On Switch contacts and make sure they are not incorrectly configured or damaged as this could be causing the no spark situation.

      • The magnet on the flywheel seems strong, but is it possible the magnet has weakened to the point it no longer creates an electrical current?

        • Hi

          It is highly unlikely that the magnets have weakened enough to no longer create a electrical current. The problem is most likely related to incorrect wiring or a problem specific to the circuitry of the generator.

  34. I unplugged the coil wire to the kill switch to isolate the electronics and still no spark.
    Purchased a new ignition coil. Still no spark.
    The old (4.89 ohms) and new coil (6.19 ohms).

    I’ve replaced the fuel valve, spark plug and ignition coil so far. What else can I replace?

  35. I’ve gained helpful info from here a couple of times so I should make it official and join up.
    Thank you!

    I’m working on about a 20 year old portable generator with a 195432 model B&S 8.5 hp motor. I have two of them that were gifts. One has been run occasionally to keep it ready for power outages. The other has never been run.

    I started the one we have been using and it was so rich, you couldn’t stand it, so I rebuilt it with a new carb kit and new plug and filters. It started right up after that and ran much better, but then just shut off and won’t start. There is no spark. I checked the on-off switch and pulled the kill harness off with no success. Checked the coil/magneto and have 2.5 ohm between spark plug terminal and housing and 0 to cut-off terminal.

    Just for grins, I dug out the other identical generator and that had spark, but very weak orange spark. So I took that coil off and put it on the one that had been running. Now no spark with that coil!. That coil has identical test readings, I sanded all contact and pick-up areas and am testing with the kill wire plug disconnected. Clearance to magnet is .010” What could I have screwed up?

    Is it possible I have tow bad coils? I can get a new coil Monday $48.00, but hate to just throw parts at it

    Now I’m stumped and we’re supposed to be having an ice storm tonight.

    Any help would be appreciated

    Thanks

  36. Hi, i have a Briggs & Stratton 13,5 OVH and I need to replace the sparkplug-connector (don’t know the name..) I have two of them. One with 1k ohm and one with 5k ohm. What ohm should i use?

    • Hi Henning

      I am assuming you need to replace the spark plug boot. I would use the one with 1Kohms as it will provide a better spark. If it is the ignition coil you are replacing then I cannot tell which is the best choice as we do not know the normal reading of coils for that motor.

  37. Hi. Appreciate your keeping this thread alive, and all the help offered.

    I’m another one with no spark. Series 1150, in a generator, bought around 2014. Checked the original coil: 5.7kohm from plug wire to ALL of kill tab, coil body, and engine block (with coil airgapped at 0.01″ (0.25mm), kill switch disconnected). Bought a new coil, no spark. Gives same readings. With them off the motor, both coils give 1.6 ohms kill switch tab to coil body…close enough to a hard short to not matter.

    If the kill tab is hard shorted to the coil body, and the coil body is not isolated from the engine when mounted, then it seems to me the coil cannot possibly work, the coil is grounded to the block at all times, it’s like leaving the kill switch permanently in “kill” position.

    So far as I can see the coil can only supply a spark if the coil body is isolated from the spark (and thus from the kill tab). Something wrong with my reasoning? Incidentally, I have a good quality DMM and know how to use it, that’s not the issue).

    Appreciate your feedback.

    • YOU ARE CORRECT. IF THE KILL TAB is SHORTED (shows CONTINUTITY) to the metal BODY of the coil, the coil is DEFECTIVE.

  38. Hello and thank you all for the useful insight. I have a briggs and stratton motor on a roto-tiller. It was working last year and this year is not 🙁

    The coil measures 2.5 K however I can’t get a spark. I noticed that the armature also has some sort of plastic device with a coil inside. Could this be causing the issue? I can’t figure out what is this for. The part number in the manual is 394970.
    Thanks a lot for your help!!

  39. Just received brand new B&S #590454 from Amazon seller. Ohm reading from ignition plug wire to body is 6.17k ohms, which exceeds the guidance of 2.5-5.0k ohms. Is this an issue?
    Kill tab reads 0.0k ohms. Thanks

    • Hi Rick

      Reading is dependant on the coil It would need to be the same model as this to have the same spec. If the coil is different or newer it may have a different acceptable range

  40. I’ve just learned that there are different magneto/ignition coils for the same engine depending on its starting mode. That is whether the engine has Recoil start verses key/electric start. I found this out after trying to use an ‘S’ designated coil (for a key-start engine) on my recoil start Kohler CV14 engine. Does anyone know what the difference between these two types coils?

  41. The proper test of any ignition coil is:
    Secondary coil reads between 2 and 20khoms
    Primary coil 1.2ohm possible 4ohms (between kill switch and body) if shows 0ohms primary its shorted and there will be impossible to start.
    Logic to switch off the engine you short the primary coil with the ground. LOL .

  42. I have a Briggs and Stratton 5HP 4-stroke engine which is fitted to a Rover Shredder mulching machine. Like some of the other commenters in this website, I have a problem with “no spark”. Just a few days ago I used the machine, but it was not easy to start on that occasion, and the spark was very weak.
    The magneto on my machine has an electronic ignition trigger incorporated into it, so there is no contact breaker or condenser which could require adjustment or replacement. I have been wondering whether the problem is actually in the electronic ignition component.
    After attempting to research, and hopefully solve the problem, I have had an idea which may help to determine whether a coil is good or not. The magneto has two coils, which are referred to as the primary and secondary coils. The primary coil has a comparatively small numbers of turns of copper wire (probably in the region of a few hundred turns), and should have a resistance of maybe 1 or 2 Ohms. The secondary coil has very many turns of much thinner copper wire (probably quite a few thousand turns) and should have a much higher resistance, typically in the range of 5 thousand Ohms. In essence, these two coils constitute a transformer, in which a small voltage applied to the primary coil can produce a very high voltage in the secondary coil, which can cause an electric spark to jump across the air gap in a spark plug. It is important that these coils are electrically isolated from the body of the magneto, in the same way that the coils in a transformer are isolated from the iron core of the transformer.
    I have performed a test, in which I removed the magneto from the engine, and mounted it on a wooden test-bed. With the spark plug attached to the high voltage lead, and the base of the spark plug electrically connected to the ground wire end of the high voltage coil, I then momentarily connected the primary coil leads to a 12 volt supply. If the ground wire lead of the primary coil is connected to one terminal of the power supply, and the other end of the primary coil is momentarily touched to the other terminal of the power supply, then sparks will be produced at the spark plug if the coils are good.
    In my case, I performed this test with the electronic ignition module disconnected from the magneto coils, and had a strong spark at the spark plug. When the electronic ignition module was included in the circuit, the spark was very much weaker. I do not know what voltage is induced in the primary coil when the magneto is functioning normally, and I do not know whether using a 12 volt supply is the most appropriate for a test such as this. I did repeat this experiment with a 6 volt power-pack as the power source, and was able to produce a spark at the spark plug. The reason why I am giving these details is to provide a simple and certain way of determining whether the coils are working. I hope that someone may have access to good technical information on what is the most appropriate voltage to be applied to the primary coil circuit.
    If the real cause of my problem is the electronic ignition trigger circuit, then I would appreciate information on how this may be resolved and repaired.

  43. I have a B&S 7hp horiz shaft engine, good spark but it kicks back too badly to start, coil tests OK BUT the kill wire to frame of coil (off engine testing) is zero ohms or a dead short so to speak. In this case is the electronic trigger in the coil toast and would that cause the spark to fire MUCH too soon? Thanks for any advice..

    • Kicking back is usually caused by a sheared or broken flywheel key which throws off the timing of the ignition.

  44. Having problems getting g a spark on an old Briggs 18hp twin cylinder engine. Pulled the plugs and kill wire yet no shock when holding either plug wire with one hand, touching ground with same hand and rotating the flywheel. It uses a 2 wire coil so testing from plug wire end to ground shows zero. I’m assuming the coil is bad and ordered a new one but it would be nice to know how to test a 2 wire coil. Anyone?

  45. I purchased a mower from a box store that had been returned. It has never cut grass because it would not start. After some trouble shooting, I did get it running by disconnecting the kill wire connection at the coil, but then, you can not kill it. The brake pad will not stop the engine, but slows it down enough that by pushing the primer bulb, I guess it “floods it” and stops it. When I test the continuity of the kill wire tab to any ground, It has continuity, so, it is always grounded? If I connect the wire (which has no shorts or problems) it will not run. If I disconnect the kill wire, it runs. Bad coil from the factory?

    • Hi Gary

      The wire from the coil usually connects to a mechanism that grounds the wire only when the throttle is in the off position, I would check that mechanism at the other end of the wire for faults. Otherwise a simple solution is to just install a simple rocker switch between the coil and the wire so you can easily turn the mower on and off with the switch.

  46. Hi I just bought a new b&r coil nr 591749 211013
    I replaced the old ony because I did not get any spark
    I run the engine for 5 min and now there is no spark again
    I din measure the resistance to 5.9 k ohm.
    What can go wrong since the new coil seems to be finished. My engine is a 6.5 hp sn 122602 0195 e1 051220
    Has my coil burned out so quick?
    Between kill contact and frame is zero ohm 0.0 between kill and spark plug is 5.9 k ohm

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