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Ignition Coils

Discussion in 'XJ Technical Chat' started by ralden96, Sep 9, 2023.

  1. ralden96

    ralden96 Member

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    Working on another 81 seca 550 and have no spark. The only electricals that I can say for sure that are not working are the backlights behind the gauges (all the other "idiot" lights work) and the headlight, which I expected not to know about as it is not running. When I checked resistance on the coils the primary read 6 ohms (200 scale) and secondary gave me nothing. It may only be 1 of several problems but I am thinking my coils have failed. Picked up a used set which were supposedly tested and working (not happy with the seller as they could not tell me there reliable test) but the reading on those is the same. Would be really frustrating to go through the hassle of swapping bad coils for bad coils. I followed videos and the manual to test both sets. Does someone have a better way to check coils? TIA
     
  2. Rooster53

    Rooster53 Well-Known Member Premium Member

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    Give us more details about how you are testing the secondary resistance. Do you have spark plug caps on, are you measuring from cap to cap, what scale is the DMM set to?

    DMM should be 200K scale with caps on and you should be measuring cap to cap or wire to wire if you removed the caps - 20K scale should work if you have the caps removed
     
  3. ralden96

    ralden96 Member

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    Coils are out of the bike. Primary resistance is being tested through the two harness leads with a DMM, 200 ohms scale and I am getting a reading of 6 ohms. Secondary being tested through the two spark plug caps with the DMM on a 20k scale. Reading may flash something around 16k but not consisitent, typically stays at 1. I have had a second set of hands to make sure contact is decent but no luck. Is there a better way to bnch test the coils?
     
  4. Rooster53

    Rooster53 Well-Known Member Premium Member

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    20K scale is not going to work with the caps on as the caps are 10K each, so expected resistance will be around 31K - use the 200K ohm scale with caps or just take them off and measure each component. I prefer to start with caps on as it might identify a poor connection between the cap and wire


    https://www.xjbikes.com/forums/threads/the-ultimate-relay-switch-sensor-and-diodes-guide.27543/

    "XJ550 models:

    Spark plug caps:
    10K +/- 20% = 8,000 to 12,000 ohms per cap acceptable range"
     
  5. ralden96

    ralden96 Member

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    Appreciate the input but isn't it a bit of a moot point if the primary is already out of spec? Shouldn't I be checking that first?
     
  6. Rooster53

    Rooster53 Well-Known Member Premium Member

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    Well if you think you have four bad coils I would question the test equipment or technique. Now you didn't say specifically but if the two original coils are 6 ohms on the primary and the new ones are 3 ohms then yes the originals are likely trash.

    Doesn't really matter which is done first, a fail on either side means a repair or replacement. You mentioned testing the secondary using the 20K scale and I just tried to help by telling you that you needed the 200K scale on the meter if the caps were still installed
     
  7. ralden96

    ralden96 Member

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    I'll try the 220k. Still haven't figured itout.
     

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