I've never had an engine issue resolved with a fresh spark plug. Do these things actually wear out?
Spark plugs?
- Thread starter Easy Livin’ 3000
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I think that's a loaded question with a few different answers depending on the application, but simple answer yes.
I've got a ~220hp 800cc twin cylinder turbocharged 2-stroke snowmobile that runs 8psi of boost on 100LL fuel (avgas). Over time it will develop lead deposits on the insulator from the fuel and can cause the spark plug to short to ground. Effectively rendering the spark plug useless.
I've also got a 215hp 1.5 liter supercharged 3 cylinder rotax engine in a 13ft shallow water jet boat that wears out spark plugs. Due to the boost pressure the engine runs a high energy ignition system to overcome the extra resistance caused by boost. This accelerates wear on the plug electrode widening the plug gap, eventually causing misfires.
Now both of these are extreme examples of when performance is desired over part longevity, but i think you get the point.
For a 2-stroke applications the common mode of failure is either fuel/oil fouling or electrically conductive deposits shorting out the plug.
Now on a typical 4-stroke application where there is no consumable lubrication oil, and the air fuel ratios are tightly controlled, spark plugs last a long time. Particularly in automotive applications most spark plugs will last well beyond 60,000 miles. Many of these application also use precious metal electrodes such as platinum and iridium to substantially slow electrode erosion.
I've got a ~220hp 800cc twin cylinder turbocharged 2-stroke snowmobile that runs 8psi of boost on 100LL fuel (avgas). Over time it will develop lead deposits on the insulator from the fuel and can cause the spark plug to short to ground. Effectively rendering the spark plug useless.
I've also got a 215hp 1.5 liter supercharged 3 cylinder rotax engine in a 13ft shallow water jet boat that wears out spark plugs. Due to the boost pressure the engine runs a high energy ignition system to overcome the extra resistance caused by boost. This accelerates wear on the plug electrode widening the plug gap, eventually causing misfires.
Now both of these are extreme examples of when performance is desired over part longevity, but i think you get the point.
For a 2-stroke applications the common mode of failure is either fuel/oil fouling or electrically conductive deposits shorting out the plug.
Now on a typical 4-stroke application where there is no consumable lubrication oil, and the air fuel ratios are tightly controlled, spark plugs last a long time. Particularly in automotive applications most spark plugs will last well beyond 60,000 miles. Many of these application also use precious metal electrodes such as platinum and iridium to substantially slow electrode erosion.
Update:
Spent $3 on a new NGK plug, and the old girl started right up. It was high time, the plug that was in it when I bought it, wasn't even the correct one.
Good thing, cause I just spent $26 on two new PTO belts.
Can't be sure the coil isn't going bad, because it was hot when it wouldn't start. But after fretting about correct torque, etc., I'm just gonna enjoy my success getting it running again!
Spent $3 on a new NGK plug, and the old girl started right up. It was high time, the plug that was in it when I bought it, wasn't even the correct one.
Good thing, cause I just spent $26 on two new PTO belts.
Can't be sure the coil isn't going bad, because it was hot when it wouldn't start. But after fretting about correct torque, etc., I'm just gonna enjoy my success getting it running again!
I might get grief over this, but I buy most anything but a Champion. For small engines, I get great service from NGKs.
I've never changed a spark plug on a small engine. I'm young though, all my small engines are 7 or 8 years old.
Interesting your comment on Champion. My father-in-law was a life long automotive repairman. He and all his circle of mechanics hated champion plugs. They would change them out anytime they saw one. Only other thing they were so adamant on was Kendall Cup oil. Nothing else would go in their fleets. That was before synthetic was affordable.
I would have to agree as well. I had an F150 that wouldn't run on brand new Champion plugs, thought it was a coil, but the dealer suggested motorcraft plugs first. I put them in and it ran until I sold it to my brother. He then ran it until he sold it.
I have never had an issue with an NGK though, they go in everything I own.
Medic21
Minister of Fire
Funny thing about spark plugs. Every manufacture designs their spark plug for their motor. Motocraft, AC Delco, Mopar, etc are the OEM for those engines. When AC Delco or champion have a plug listed for a Ford it’s a comparable heat range but not the correct heat range. It works but, not optimal.
I change plugs in all my small engines yearly when I change oil and service them. Especially the chainsaws, new air filter is the time to do a new plug. That can be the difference when it’s 10 degrees out with it starting or not.
brenndatomu
Minister of Fire
semipro
Minister of Fire
As someone who literally has changed thousands of spark plugs as an auto mechanic I rarely find the need to replace those in my personal fleet of infernal combustion engines, even vehicles.
That said, I recently had a weird no start/misfire in a John Deere mower with a Kawasaki engine. I checked compression, valves, fuel system, everything , or so I thought. The plug looked fine but I (finally) replaced it and fixed the problem. I then remembered how I'd washed the engine recently when it was still warm. I'm now sure I cracked the plug's ceramic insulator with thermal shock from the cold water. I've also seen spark plug insulators cracked from installation causes. The lesson learned was that even a clean plug with great looking electrodes can cause problems.
If you're having problems I suggest you start with a plug, they're cheap and easy. Carbs, valves, compression -- they're much tougher to deal with. I also avoid Champion and like NGK, Denso, or Bosch.
That said, I recently had a weird no start/misfire in a John Deere mower with a Kawasaki engine. I checked compression, valves, fuel system, everything , or so I thought. The plug looked fine but I (finally) replaced it and fixed the problem. I then remembered how I'd washed the engine recently when it was still warm. I'm now sure I cracked the plug's ceramic insulator with thermal shock from the cold water. I've also seen spark plug insulators cracked from installation causes. The lesson learned was that even a clean plug with great looking electrodes can cause problems.
If you're having problems I suggest you start with a plug, they're cheap and easy. Carbs, valves, compression -- they're much tougher to deal with. I also avoid Champion and like NGK, Denso, or Bosch.
Last edited:
XmasTreefarmer
Feeling the Heat
I've had a new plug "fix" things several times over the years - it's my first "go to" here on the farm (except maybe making sure it's got gas
)
I have at least one of every plug that I need for my equipment on hand. My wife teases me that it's part of my, "on farm hardware store". When I need to get something done, I really need to get it done and swapping out a plug has saved me a couple of times and as someone mentioned - it's a very inexpensive thing to try. If it doesn't solve the issue, as you continue to trouble shoot, you at least know it's not the plug!
) I have at least one of every plug that I need for my equipment on hand. My wife teases me that it's part of my, "on farm hardware store". When I need to get something done, I really need to get it done and swapping out a plug has saved me a couple of times and as someone mentioned - it's a very inexpensive thing to try. If it doesn't solve the issue, as you continue to trouble shoot, you at least know it's not the plug!
I aspire to having an "on farm hardware store"! I find great satisfaction from not having to run to town to get something. My biggest obstacle is my horrendous organizational skills, and a memory that gets worse every day. So far, I usually am able to find stuff when I need it, but sometimes even that is a major project.I've had a new plug "fix" things several times over the years - it's my first "go to" here on the farm (except maybe making sure it's got gas
I have at least one of every plug that I need for my equipment on hand. My wife teases me that it's part of my, "on farm hardware store". When I need to get something done, I really need to get it done and swapping out a plug has saved me a couple of times and as someone mentioned - it's a very inexpensive thing to try. If it doesn't solve the issue, as you continue to trouble shoot, you at least know it's not the plug!
XmasTreefarmer
Feeling the Heat
Hey 3000!
I got a good chuckle out of your reply! I have some up with a few "systems" that seem to work for me, because I suffer from all of the same things that you do!
I tried what I'd call "inventory lists" and that was a disaster. That never seemed to get updated - so sometimes it looked like I had what I needed, but didn't and visa versa. I now organize by "type". I have a small shelf of spark plugs. That is the only place that I have them, so that's the only place I have to look. When I use 1 or 2 or 4, I save the boxes in my pocket and then I order them in the next few days. Having a box or two sitting on my desk is a good reminder. Then I have all things for each piece of equipment together: the oil filters, air filters, and belts for the DR mower are all together, same for the push lawn mower, lawn tractor, etc. When I need something, I just go to that part of the barn where stuff is on shelves and hanging. Many years ago I added small shelves between the studs in the barn - one of the smartest things I've ever done except marrying my wife (which is what she tells me!).
I got a good chuckle out of your reply! I have some up with a few "systems" that seem to work for me, because I suffer from all of the same things that you do!
I tried what I'd call "inventory lists" and that was a disaster. That never seemed to get updated - so sometimes it looked like I had what I needed, but didn't and visa versa. I now organize by "type". I have a small shelf of spark plugs. That is the only place that I have them, so that's the only place I have to look. When I use 1 or 2 or 4, I save the boxes in my pocket and then I order them in the next few days. Having a box or two sitting on my desk is a good reminder. Then I have all things for each piece of equipment together: the oil filters, air filters, and belts for the DR mower are all together, same for the push lawn mower, lawn tractor, etc. When I need something, I just go to that part of the barn where stuff is on shelves and hanging. Many years ago I added small shelves between the studs in the barn - one of the smartest things I've ever done except marrying my wife (which is what she tells me!).
Stelcom66
Minister of Fire
Re:
Re: memory/inventory - on my computer's PIM (Personal Information Manager, important date reminders, notes, etc.) I have a category titled 'Inventory'. In there I'll enter where I've put things that aren't used often or rarely used such as the spare key and shear pins for the snowblower. Another example is one of those Velcro arm braces that I got a few months ago but (fortunately) don't need now. I had one in 1994 when I was officially diagnosed with 'Tennis elbow' - it has to be in the house somewhere, never found it so bought another one.
Also I keep notes on parts and repairs. Just today I referred to notes on the chainsaw. I replaced the chain in just a few minutes unlike last time. I should have known better, this time I kept the saw upright - last time had it on it's side.
As for spark plugs - I also don't think a replacement has ever resolved a non starting or poorly running engine for me. My chainsaw wouldn't start this fall, same with the new plug and cleaning the carburetor. Then, for some unknown reason it started the next weekend and has been fine since.
Hey 3000!
I got a good chuckle out of your reply! I have some up with a few "systems" that seem to work for me, because I suffer from all of the same things that you do!
Re: memory/inventory - on my computer's PIM (Personal Information Manager, important date reminders, notes, etc.) I have a category titled 'Inventory'. In there I'll enter where I've put things that aren't used often or rarely used such as the spare key and shear pins for the snowblower. Another example is one of those Velcro arm braces that I got a few months ago but (fortunately) don't need now. I had one in 1994 when I was officially diagnosed with 'Tennis elbow' - it has to be in the house somewhere, never found it so bought another one.
Also I keep notes on parts and repairs. Just today I referred to notes on the chainsaw. I replaced the chain in just a few minutes unlike last time. I should have known better, this time I kept the saw upright - last time had it on it's side.
As for spark plugs - I also don't think a replacement has ever resolved a non starting or poorly running engine for me. My chainsaw wouldn't start this fall, same with the new plug and cleaning the carburetor. Then, for some unknown reason it started the next weekend and has been fine since.
Qvist
Burning Hunk
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