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  1. #1
    Veteran Member
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    Jan 2002
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    1,561
    Location
    South East Michigan
    Tractor
    New Holland TC30 Hydro 4x4, Gravely Zero Turn Mower

    Default Bad Sparkplug

    I have been troble shooting a gas engine and finally found out why it will not run. I checked for spark off the plug wire and it checked out fine. I looked at the sparkplug and it was wet but otherwise in excellent condition. I drained all the gas and rebuilt the carb. The machine would'nt start after all this even with starting fluid. Finally had the presence of mind to check the plug. Sure enough, the plug does not fire. I have never before seen a plug that will not fire that has no outward clues. How can a solid-state component like a sparkplug just stop working?

    Jerry

  2. #2
    Platinum Member
    Join Date
    Jan 2002
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    856
    Location
    South West Pa/Greene county
    Tractor
    Long/Landtrac360DTC

    Default Re: Bad Sparkplug

    Maybe it's either shorted or open internally ?

    Murphy's 3rd law, Whatever you check last will be the bad part.


  3. #3
    Gold Member
    Join Date
    Feb 2001
    Posts
    436
    Location
    Mississippi
    Tractor
    Kubota M-4900

    Default Re: Bad Sparkplug

    I wish I knew too. I have a Yamaha four wheeler that was running like a top. I parked it one day and got back on - WOULD NOT START. I tried everything, finally went to town and got a new plug and it started the first time it turned over. The plug that came out of it looked like new but it was dead.

    TBone

  4. #4

    Join Date
    Jul 2001
    Posts
    1,806
    Location
    Houston, TX.
    Tractor
    2001 TN65, 1951 8N Ford

    Default Re: Bad Sparkplug

    If it's a resistor plug the little wire in it can be burnt through. A non resistor plug can have a cracked insulator or a carbon track. I've seen lots and lots of bad plugs, even an amazing amount bad new out of the box. If your plug gets wet it won't fire. Gasoline is a hydrocarbon and the carbon part conducts electricity. If the plug is even damp the spark can run from the center electrode down the insulator to the base. If I have to troubleshoot a no start or a rough running motor I'll stick a new set of plugs in for drill. Once I started doing that life got a lot easier.

  5. #5
    Super Star Member RoyJackson's Avatar
    Join Date
    Nov 2001
    Posts
    18,746
    Location
    Bethel, Vermont
    Tractor
    John Deere 4400 MFWD, Deere 855D UTV, Z920A Zero Turn Mower and assorted implements

    Default Re: Bad Sparkplug

    I've seen bad plugs quite a bit. You should keep a spare around for any of the small gasoline engines (lawn mowers, weed whackers, snowmobiles, etc) especially if they're two-stroke engines. Number of things can cause them to malfunction...those noted above, erosion on the electrodes, gap, sooting (fouling).

    My lawn mower manual (a Wally World special) recommends changing the plug annually. I don't, of course, but I do keep a spare handy.

    BTW, it's suggested you use an anti-seize compound on the threads when you install the plugs.

  6. #6
    Veteran Member
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    Jan 2002
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    South East Michigan
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    New Holland TC30 Hydro 4x4, Gravely Zero Turn Mower

    Default Re: Bad Sparkplug

    It's a resistor type plug for a single cylinder four stroke motorcycle. I got a new plug and will put it in tonight. I expect instant gratification. [img]/w3tcompact/icons/smile.gif[/img]

    About that anti-seize compound. There are two kinds sold around here. One type is silver in color and the other type is copper in color. The auto parts people can't tell me what applications each one is intended for??? Should I use anti-seize on my auto sparkplugs also? (the heads are aluminum)

    Jerry

  7. #7
    Super Star Member RoyJackson's Avatar
    Join Date
    Nov 2001
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    18,746
    Location
    Bethel, Vermont
    Tractor
    John Deere 4400 MFWD, Deere 855D UTV, Z920A Zero Turn Mower and assorted implements

    Default Re: Bad Sparkplug

    "There are two kinds sold around here. One type is silver in color and the other type is copper in color. The auto parts people can't tell me what applications each one is intended for??? Should I use anti-seize on my auto sparkplugs also? (the heads are aluminum)"

    Your plugs are steel, your heads (for the scoot and the car) are aluminum. What can result is <font color=red>dissimilar metal corrosion</font color=red>. This is where one metal "sacrifices" itself for the other. You get anodic/cathodic reactions. The best example I can think of is for boat owners: You install and periodically replace "sacrificial anodes".

    It's a good idea to anti-seize any thread (engine manifold and other bolts or studs, wheel bolts and studs).

    I use the silver stuff, by the way. I've seen the copper colored anti-seize, but I never read the label.

    If you don't have any anti-seize handy, you can use oil (motor oil or something of that nature), but it's not as good.

  8. #8

    Join Date
    Apr 2002
    Posts
    280
    Location
    Rindge, NH
    Tractor
    Kubota L48 (Ellie Mae)

    Default Re: Bad Sparkplug

    Just in case you've never used anti-sieze before - a (very) little bit goes a long way. a very long way. All you want is enough to color the threads.

    -david

  9. #9
    Veteran Member
    Join Date
    Jan 2002
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    1,561
    Location
    South East Michigan
    Tractor
    New Holland TC30 Hydro 4x4, Gravely Zero Turn Mower

    Default Re: Bad Sparkplug

    Yep, that did it. The bike is now running better than ever [img]/w3tcompact/icons/smile.gif[/img]

    Jerry

  10. #10

    Join Date
    Apr 2001
    Posts
    388
    Location
    Southern Maryland
    Tractor
    L3010DT

    Default Re: Bad Sparkplug

    <font color=blue>Just in case you've never used anti-sieze before - a (very) little bit goes a long way. a very long way. All you want is enough to color the threads.</font color=blue>

    Ain't that the truth. I have a love hate relationship with the stuff. It works great, but it gets EVERYWHERE. Between anti-seize and kroil, there is no excuse for seized bolts these days.

    Nick

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