Is my problem the spark plug?

[Backstage]

So you hear this EVERYWHERE. “My chainsaw (or any other small engine equipment) wouldn’t start, so I tried changing the spark plug!”

I’ve never had this be the root cause of a problem. Clogged intakes, poor fuel, leaks, bad tuning…sure! You might pull a spark plug and be amazed at how it’s running with such a gunked up part, but if anything, it’s telling a story about another problem. Hit it with a brass brush and put it back in, then fix the actual problem!

How often have you had just changing the plug fix a starting problem? Curious if I live in some kind of micro-universe with different rules.

 

[Lionsfan]

I had one go bad out of the blue in my 365 xtorque. About the only time I can think of honestly.

 

[RedneckChainsawRepair]

Several times. Some were even new NGK that was bad right out of the box.

 

[Okie]

I've had it happen to me in both chainsaws and Briggs 3-5 hp engines.
Usually a Champion J6 or J8.

If you ever work on a pic4ece of equipment for several days (thinking you are really a good top of the line whizzo mechanic) and then replace that little measley spark plug and it fixes the problem, it will jerk the wind out of your said AND YOU WILL NOT EVER FORGET SUCH.

Yep, I lived in that micro universe at one time.
I actually saved couple of them little bad ones. They really look clean and good when eyeballing.
I'm hoping I can get to install them bad plugs into some hot shot mechanics chainsaw one of these days and monitor the outcome. I suspect I might get a good buy on a bad chainsaw, blaming low compression.

 

[slimbo3006]

I chased a poor running engine once where I turned the carb needles every way possible and could not get any consistency. Finally went to pull the plug to look at it and do a comp check. It was literally broken in half. Just held together and in place by the short coil wire. Needless to say...that fixed the problem. It was a champion CJ7 or 8 if I remember right. No idea what caused it.

 

[cookies]

I see bad spark plugs all the time. Small equipment will not start or starts and runs until it warms up then bam shuts off. I see cars/trucks all the time with bad plugs causing misfires and burning up ignition coils.
The standard copper core spark plug used in a oil/air cooled engine is rated for replacement at 400 hours. I replace them at every service on other peoples equipment because thats only 2.5 months pulling a 40hr work week.
In a liquid cooled automobile engine a copper core is rated for 30,000 miles or 3 years witch ever is first because it runs cooler. Very few still use a copper core plug from the factory still.
You can take a ohm reading of the internal resistor to check integrity, should be in ball park of 4800-5,000 ohms.

 

[OM617YOTA]

I bought a no run Generac for cheap. Wouldn't even cough until I put a new plug in it, then it wouldn't stay running until I put a new oil pressure switch in it. Flipped it for several hundred percent profit.

That's the only plug I've had go bad.

 

[OM617YOTA]

Several times. Some were even new NGK that was bad right out of the box.

Make sure you got a legit NGK. NGK even has a counterfeit identifying page on their website. Buy from eBay or Amazon, who knows what you really got.

 

[cookies]

Amazon and ebay are ripe with counterfeit products, never purchase spark plugs off either site instead get them from a store or order them from a parts supply company that has stores near you.

 

[KASH]

I would say between outboards snow machines lawn mowers chain saws and all the other equipment I own I probably have had several hundred bad plug failures.This was more of a problem in points equipped engines and the problem in some cases was probably dirty or corroded points.
Kash

 

[Captain Bruce]

So you hear this EVERYWHERE. “My chainsaw (or any other small engine equipment) wouldn’t start, so I tried changing the spark plug!”

I’ve never had this be the root cause of a problem. Clogged intakes, poor fuel, leaks, bad tuning…sure! You might pull a spark plug and be amazed at how it’s running with such a gunked up part, but if anything, it’s telling a story about another problem. Hit it with a brass brush and put it back in, then fix the actual problem!

How often have you had just changing the plug fix a starting problem? Curious if I live in some kind of micro-universe with different rules.

I have a dozen saws come in a week. The odd fella will question the shop rate; given that all it needs is a new spark plug. The machine goes straight back in their truck.

Carb issues, poor fuel quality, dirty gas cans, clogged air filters, will forever ignore a clean $5 spark plug.

 

[Joisey]

I had one spark plug truly fail on me in my Homelite XL2. A Champion DJ7J. I had just filled the fuel and oil tanks and when I turned the saw sideways with the recoil side of the saw facing basically upright the saw would stall. Put the saw on the ground, one pull and it started and ran fine until I turned it with the recoil start facing upward. Recoil start side facing downward the saw ran fine, as it did with the saw oriented as it would be on the ground.

On a whim I removed the spark plug to check it. It had been in the saw for a few years, showed no wear and was a nice light chocolate brown. I went to check the gap with my wire gauges and there was no gap between the electrodes. When I turned the plug with the threads facing down the gap was correct.

It seems the insulating material that is used to bond the insulator to the shell gave way over time and allowed the insulator and center electrode to move in the outer shell. I still have the spark plug in a drawer somewhere.

Perhaps the reason why replacing the used spark plug with a new unit is that the new plug fires easier because of the sharp edges on the electrodes, helping a possibly marginal ignition system to allow the saw to start.

 

[cookies]

I had one spark plug truly fail on me in my Homelite XL2. A Champion DJ7J. I had just filled the fuel and oil tanks and when I turned the saw sideways with the recoil side of the saw facing basically upright the saw would stall. Put the saw on the ground, one pull and it started and ran fine until I turned it with the recoil start facing upward. Recoil start side facing downward the saw ran fine, as it did with the saw oriented as it would be on the ground.

On a whim I removed the spark plug to check it. It had been in the saw for a few years, showed no wear and was a nice light chocolate brown. I went to check the gap with my wire gauges and there was no gap between the electrodes. When I turned the plug with the threads facing down the gap was correct.

It seems the insulating material that is used to bond the insulator to the shell gave way over time and allowed the insulator and center electrode to move in the outer shell. I still have the spark plug in a drawer somewhere.

Perhaps the reason why replacing the used spark plug with a new unit is that the new plug fires easier because of the sharp edges on the electrodes, helping a possibly marginal ignition system to allow the saw to start.

More often a worn out plugs internal resistor will have higher ohms, this leads to coils being over worked burning them up or resulting in erratic or poor spark quality. I get them by the shop 10 piece pack costing under 2.50 a plug.

 

[Burning man]

So you hear this EVERYWHERE. “My chainsaw (or any other small engine equipment) wouldn’t start, so I tried changing the spark plug!”

I’ve never had this be the root cause of a problem. Clogged intakes, poor fuel, leaks, bad tuning…sure! You might pull a spark plug and be amazed at how it’s running with such a gunked up part, but if anything, it’s telling a story about another problem. Hit it with a brass brush and put it back in, then fix the actual problem!

How often have you had just changing the plug fix a starting problem? Curious if I live in some kind of micro-universe with different rules.

Learned from my dad and grandpa to keep a couple extra spark plugs for the saw, if you flood the saw just switch the plug and if one gives up you've got a spare or 2. I'll never buy E3 plugs again, I ended up replacing the ones I bought with some old crusty ones that still worked.

 

[PEK]

I learnt not to trust even a new plug, always carried 2 in the boxes in a tin and in that tin was a spare bar nut and a length of starter cord, funnilly enough I have rarely had to use them, just as the tow rope and jump cables I keep in the truck have helped many out.

 

[RedneckChainsawRepair]

Make sure you got a legit NGK. NGK even has a counterfeit identifying page on their website. Buy from eBay or Amazon, who knows what you really got.

Legit right from dealers bulk. Why I swore them off for years too. Went to just German made Bosch.

But now days it dont matter. They all are made everywhere. Even NGK is made in China and every other 3rd world country too.

 

[Old2stroke]

The GM Corvettes with the new aluminum engine starting in 1997 all came with double platinum plugs and the tiny platinum puck welded to the ground electrode had the habit of falling off. I change mine to NGK and doubt that GM has done anything to recognize or fix the problem. With small engines, in the last 20 or so years I have only had one bad plug, center insulator came apart from the metal base.

 

[67L36Driver]

I have a pile of used plugs on my bench. Most all are greasy black on the end. They were the wrong plug for the application and not really ‘bad’, just too cold a heat range.

Only had three actually bad plugs. One Champion and two Bosch, the center electrode had come loose and slid down against the ground.

 

[RedneckChainsawRepair]

In our repair group lot of reported problems with ngk doing that too. All plugs really do it.

One was sliding to ground it when turned over how it suppose to be. Then several like this NGK.

 

[hotshot]

I would say between outboards snow machines lawn mowers chain saws and all the other equipment I own I probably have had several hundred bad plug failures.This was more of a problem in points equipped engines and the problem in some cases was probably dirty or corroded points.
Kash

That’s crazy, hundreds?, I never had a new bad 2 stroke plug failure in over 50 years.

That does NOT include normal maintenance like worn electrodes &/or carbon fouling from running too rich.

Sounds more like some auto customers stating that they had ‘bad brake pads’ or even bad rotors when they’re simply worn out…