Bad Sparkplug

   / Bad Sparkplug #1  

Mrwurm

Veteran Member
Joined
Jan 20, 2002
Messages
1,561
Location
South East Michigan
Tractor
New Holland TC30 Hydro 4x4, Gravely Zero Turn Mower
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
 
   / Bad Sparkplug #2  
Maybe it's either shorted or open internally ?

Murphy's 3rd law, Whatever you check last will be the bad part.
 
   / Bad Sparkplug #3  
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
 
   / Bad Sparkplug #4  
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. :)
 
   / Bad Sparkplug #5  
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.
 
   / Bad Sparkplug
  • Thread Starter
#6  
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. /w3tcompact/icons/smile.gif

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
 
   / Bad Sparkplug #7  
"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.
 
   / Bad Sparkplug #8  
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
 
   / Bad Sparkplug
  • Thread Starter
#9  
Yep, that did it. The bike is now running better than ever /w3tcompact/icons/smile.gif

Jerry
 
   / Bad Sparkplug #10  
<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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