Is my problem the spark plug?

[KASH]

In looking back it is probably a higher number I changed out.With the old snow mobiles the heavy oil mix and bitter cold caused many many plugs to fail most people threw them away but I burnt mine with a propane torch and cleaned and gapped them.
The reason the machine would not run or only ran on one was a failed spark plug.
The problem of the plug being fouled was not the fault of the plug but other factors causing it to malfuntion.
t
Truth be told I can only remember a half dozen or so that were faulty last summer it was an NGK in my wifes 20hp Yamaha it worked fine at low speed but had a miss at high speed.
Kash

 

[ballisticdoughnut]

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 was a auto tech for over a decade. Now a small engine tech. I’ve seen my fair share of spark plug problems. I’ve been working on engines even before I could legally drive. I couldn’t tell you how many times I’ve heard people say “it must be the spark plug”. Well, no. It most likely isn’t. I’d say you have a single digit percentile the spark plug is actually the problem.

 

[whitepine2]

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

Same here new plug junk and another go after short time. I always go for the easy way out and if changing out a plug works that's fine with me.

 

[sean donato]

Seen plenty of bad plugs, I don't personally care if it's carbon fouled or not, it don't spark its junk. Used to be normal to keep a few spare plugs in the sleds/bikes. Can't say I've ever had real issues with them in saws, typically check them and if all looks well, stuff them back in. Think the worst plug issue I ever had was my little Honda powered push mower. Got it for free. It ran, but as soon as you pushed it into any grass it would stall right out. Really pulled my hair out on that one. Had spark through a ignition tester. So coil was good. It ran to full rpm, but as soon as load was applied it would choke itself right out. My wife was actually the one that asked if I changed the spark plug? Said nope, went and grabbed a new one oit of the house and tossed it in. Problem solved. (Mind you her dad is the its a plug problem guy, so thats what she says no matter what's actually wrong.)
Vehicles get new plugs every 50k miles. Most of mine have iridium plugs. Can't say I've ever had an issue with them.
I prefer ngk plugs, but still have a few Bosch kicking around, as well as a few champions for the old kohlers, vehicles get autolite plugs. Never had an issue with getting plugs off the internet, Napa wants 3 tines the price and it's easy enough to verify its a genuine plug.

 

[Tony Mayhew]

I play with 2-stroke engines almost every day! I own about 70 chainsaws and half of them are vintage homelites. The guy who goes by 67L36 driver is absolutely correct! Heat range plays a major role in how the saw is going to run. That plug that is too cold may have worked when the temperature was 85 and little humidity, But as I have learned through trial and error living in Portland Oregon, When it rains like hell or its 25 degrees outside, Now you're dealing with a different animal. Figure it like this guy! If a 2-stroke doesn't like burning the oil thats mixed in the fuel very easy, Then go ahead and throw in about 85-90 percent humidity on top of that and you got yourself a PIA to get things burning properly. This is how I do it and it fires up every time! Or if it starts and then dies again I can at least take compression and fire out of the list of things that will keep it from running, Because that told me that it is a fuel related issue But nine times out of ten the sparkplug is fouled! Because this is what happens. You tried to start it without success, So here comes your neighbor who thinks he can get it started, So he pulls and pulls and pulls! All this time contributing to the problem! I have a rule that it doesn't fire up after four pulls then don't pull it a fifth time. Stop, pull the plug and read what it's telling you! And there is always a couple of cry baby's that comment back, ( Oh! You can't do that! ) I'm telling you no lies! Yes you can! I take a BernsOmatic propane torch and burn the wet fuel off of the electrode staying away from the ground strap as much as possible, With the on/off switch off and choke open, pin the throttle wide open and pull the engine over about 3 or 4 times to expell the old air and fuel out of the cylinder and bringing clean oxygen in the cylinder because fire loves this stuff! Now squirt one very small shot of starting fluid in the plug hole and reinstall the hot spark plug, turn the switch back on run, pull the choke all the way out and then push it back open ever so little so that it cracks it open just enough to draw some air in. Set the saw down on the ground! Very important that you do not drop start it like most idiots do! Foot in trigger section and a good firm grip on the handle bar holding it to the ground. Now pay attention to how far your pull starter rope comes out when you pull it, You wouldn't think that it could be part of your problem but you would be wrong to think that! You need no less than 38 and no more than 41 inches of rope on your spool to get a good quality pull. I see it all the time where someone has broken the rope and never replaced it and what happens is when it comes to the end it will break the plastic pieces in the pull starter assembly! One good pull is all your gonna need and Bam!!! Old Jeds a millionaire!

 

[Tony Mayhew]

I work on small engine equipment every day! I have a chainsaw collection of around 70 saws and I am the guy in my neighborhood that everyone brings their piece of equipment to when it won't start for them. I have seen all kinds of sparkplug failures due to all kinds of different issues! Let's start with the broken electrode you are commenting on, I usually see that happen when someone has installed the wrong sparkplug with a higher heat range then it is intended to be used and the piston comes up and touches the ground strap and crushes it into the electrode! Or someone using the wrong tool for gapping the plug like a screwdriver prying against it while bending the ground strap out. Do you realize that if there is a little piece of carbon deposit that is trapped between the outer shell of the sparkplug and the electrode that it will cause the plug to short out? And here is my favorite one I see all the time! Some rookie scared of damaging the piston so he adds a little extra oil to the mix for good measure! And if it is cold out or especially if it is wet as hell like it is alot of the time in Portland Oregon, it doesn't like burning the oil thats mixed with the gas when cold, Now put 85-90 % humidity in the mix of things that will keep you from getting a 2-stroke engine started and you have a perfect reason for your sparkplug to foul! Oh, But it gets better from here! Rookie pulls and pulls trying to get it to fire to no avail! Here comes your neighbor who thinks he is a know it all and he pulls and pulls, All the while making the situation worse with each pull of the cord! I have seen it to the point that the crankcase is full of fuel where as you can turn the chainsaw upside down and the fuel will drain out of the sparkplug hole! I have a rule that I live by, and I try to teach the owner of the saw as i resolve the issue they are experiencing. If it doesn't fire in four pulls, Stop and find the reason it won't start! The majority of the time if it didn't want to fire with four pulls then it ain't going to get any better from there! I have found that taking a propane torch and putting a little heat on the end of the sparkplug and squirting a very small shot of choke and carb cleaner or starting fluid in the sparkplug hole and immediately replace the sparkplug that nine times out of ten it will fire up with one pull! And I don't care what anyone says about using this stuff or it will ruin your saw! I never seen any kind of damage resulting from this! In fact! It will tell you that if the the engine starts and then dies again that it has spark and it has compression and you can rule those two things out of your equation and start figuring out where the fuel related issue is that's accruing. And from what I have gathered is that unless you're getting a NGK sparkplug in a yellow box that says it's from Japan then you are getting a knock off from China or where ever they make them? That means that if you're getting NGK sparkplugs in a silver box they are not the real deal folks!

 

[JohnL]

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.

Back in the old days I never had issues with spark plugs. Starting in the early 2000's Champion went downhill and since then don't trust them. They don't fail completely, the engine might pop, or even catch and run badly leading you to think it's a fuel issue. I still have old Champions from the 80's and before working fine in old mowers, they cheaped out somewhere in the design on the new plugs. NGK's have never given me any problems.


I think for most non-tech people it's just that the spark plug is easy to get to and replacing it is their first go-to.

 

[jellyroll]

i run autolite plugs i have not had any issues.

 

[Howsitgoineh]

Back in the old days I never had issues with spark plugs. Starting in the early 2000's Champion went downhill and since then don't trust them. They don't fail completely, the engine might pop, or even catch and run badly leading you to think it's a fuel issue. I still have old Champions from the 80's and before working fine in old mowers, they cheaped out somewhere in the design on the new plugs. NGK's have never given me any problems.


I think for most non-tech people it's just that the spark plug is easy to get to and replacing it is their first go-to.

Ngk is the best in my opinion.

I have run plenty of saws with older champion plugs in them. Usually just a good quick clean and they are good to go!

 

[Tony Mayhew]

Ngk is the best in my opinion.

I have run plenty of saws with older champion plugs in them. Usually just a good quick clean and they are good to go!

Just remember this my good man! If the NGK sparkplug comes in a yellow box its a real NGK plug,from Japan, and if it comes in a silver/gray box its a chianiese knock off!

 

[OM617YOTA]

The Chinese are happy to counterfeit boxes too. Here's the full story, straight from NGK:

https://www.ngkntk.com/newsroom/blog/emea/fake-or-not/

 

[ballisticdoughnut]

I know there are fake NGK iridium spark plugs, I don’t think China is producing counterfeit small engine plugs. Could be wrong though.

 

[sean donato]

Just remember this my good man! If the NGK sparkplug comes in a yellow box its a real NGK plug,from Japan, and if it comes in a silver/gray box its a chianiese knock off!

Doesn't means it's from Japan. like every other company they have factories in multiple countries.

 

[sean donato]

I know there are fake NGK iridium spark plugs, I don’t think China is producing counterfeit small engine plugs. Could be wrong though.

They are, bosch too, and not just spark plugs. Glow plugs are a big issue as well.

 

[ballisticdoughnut]

They are, bosch too, and not just spark plugs. Glow plugs are a big issue as well.

Doesn’t surprise me. I’m sure all brands of iridium plugs are faked. Denso, Bosch, NGK, etc. Glow plugs are a new one for me, been out of the automotive industry for a while now.

 

[Gord404]

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.

Had a few lik that, turn them upright they look good turn them down and the gap is nonexistant- had a 365 in hear where a guy put a chineese torch plug in and abou 5 minutes the strap fell off and caused a bit of damage to the cylinder- garbage

 

[bwalker]

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.

Heat range has nothing to do with the color of the plug. A plug 3 heat ranges hotter would run no cleaner.
What you have is a tuning issue.

 

[bwalker]

I play with 2-stroke engines almost every day! I own about 70 chainsaws and half of them are vintage homelites. The guy who goes by 67L36 driver is absolutely correct! Heat range plays a major role in how the saw is going to run. That plug that is too cold may have worked when the temperature was 85 and little humidity, But as I have learned through trial and error living in Portland Oregon, When it rains like hell or its 25 degrees outside, Now you're dealing with a different animal. Figure it like this guy! If a 2-stroke doesn't like burning the oil thats mixed in the fuel very easy, Then go ahead and throw in about 85-90 percent humidity on top of that and you got yourself a PIA to get things burning properly. This is how I do it and it fires up every time! Or if it starts and then dies again I can at least take compression and fire out of the list of things that will keep it from running, Because that told me that it is a fuel related issue But nine times out of ten the sparkplug is fouled! Because this is what happens. You tried to start it without success, So here comes your neighbor who thinks he can get it started, So he pulls and pulls and pulls! All this time contributing to the problem! I have a rule that it doesn't fire up after four pulls then don't pull it a fifth time. Stop, pull the plug and read what it's telling you! And there is always a couple of cry baby's that comment back, ( Oh! You can't do that! ) I'm telling you no lies! Yes you can! I take a BernsOmatic propane torch and burn the wet fuel off of the electrode staying away from the ground strap as much as possible, With the on/off switch off and choke open, pin the throttle wide open and pull the engine over about 3 or 4 times to expell the old air and fuel out of the cylinder and bringing clean oxygen in the cylinder because fire loves this stuff! Now squirt one very small shot of starting fluid in the plug hole and reinstall the hot spark plug, turn the switch back on run, pull the choke all the way out and then push it back open ever so little so that it cracks it open just enough to draw some air in. Set the saw down on the ground! Very important that you do not drop start it like most idiots do! Foot in trigger section and a good firm grip on the handle bar holding it to the ground. Now pay attention to how far your pull starter rope comes out when you pull it, You wouldn't think that it could be part of your problem but you would be wrong to think that! You need no less than 38 and no more than 41 inches of rope on your spool to get a good quality pull. I see it all the time where someone has broken the rope and never replaced it and what happens is when it comes to the end it will break the plastic pieces in the pull starter assembly! One good pull is all your gonna need and Bam!!! Old Jeds a millionaire!

He isn't correct and neither are you. A sparkplugs heat range has nothing to do with how hot the heat of combustion is, period. Black and fouled plugs are caused by running rich and heat range has zero to do with that.

 

[stihltech]

So you are trying to make a unit run correctly but it cannot be the sparkplug? Unless it looks brand new, clean, and not a knockoff, it is part of a tune up.
But I also have to guarantee the work. Not worth the risk for the price. Same with a fuel filter.

 

[Okie]

“it must be the spark plug”. Well, no. It most likely isn’t. I’d say you have a single digit percentile the spark plug is actually the problem.

Got to watch those words most likely not.
I lot of people that think they are really good mechanics and work on a piece of eq that has only one spark plug like for example a chainsaw for several days tuning the carb, overhauling the carb, pressure testing the crankcase and then it seems they have eliminated everything EXCEPT that little old measley $2 spark plug they stick another spark plug in and surprise it runs great.
They are so great of a mechanic that they will not admit to anyone else that it was JUST THE SPARK PLUG after they spent hours or days trying to fix the equipment. They really do not want to admit it to themselves.
They want to keep it a secret because good mechanics just don't overlook simple things.
Changing the spark plug to the correct one is one of the easy things to try first but often overlooked because you are a great mechanic and do not have time to fool around with doing something simple as a fix.
I've seen a bad $2 spark plug fix a piece of eq often enough that I check the plug often when a piece of eq is not acting correctly. Really makes me feel weak upstairs if I overlook a measley little spark plug as the problem.
I've actually got some bad ones in a box labeled bad just to show people. Mostly the little j6-j8 champions that look good visually. I would like to install some of these bad plugs into some engines that are being used in a small engine mechanics class and watch the results or even a piece of eq headed for a PRO mechanic technician shop and then listen to the results of the troubleshooting procedure for a fix. Most likely the spark plug would not be mentioned.