# Spark Plug Mistery **URL:** \ **Category:** Factual Questions\ **Created:** [August 10, 2015, 11:54pm UTC](https://boards.straightdope.com/t/spark-plug-mistery/727499 "2015-08-10T23:54:47Z")\ **Posts on this page:** 7\ **Page:** 2
**Author:** ![Nefario](https://avatars.discourse-cdn.com/v4/letter/n/59ef9b/32.png) [@Nefario](https://boards.straightdope.com/u/Nefario)\ **Post date:** [August 13, 2015, 3:21am UTC](https://boards.straightdope.com/t/spark-plug-mistery/727499/21 "2015-08-13T03:21:42Z")
> [@Simple\_Mind](#): > > …as I experience myself in the past… Was that in your 40 years of repairing 2-stroke and 4-stroke engines? In your references please point to and describe the mechanism of failure you’re referring to. Also enlighten us as to how you plan to avoid it next time. Then - Problem Solved! ---
**Author:** ![Simple\_Mind](https://avatars.discourse-cdn.com/v4/letter/s/7cd45c/32.png) [@Simple\_Mind](https://boards.straightdope.com/u/Simple_Mind)\ **Post date:** [August 13, 2015, 11:19pm UTC](https://boards.straightdope.com/t/spark-plug-mistery/727499/22 "2015-08-13T23:19:41Z")
> [@Nefario](#): > > In your references please point to and describe the mechanism of failure you’re referring to. I invite you to visit me here at my place and “experience” live in a third World Country, I like it here but you may miss some “possibilities” in the way you have to solve your problems. By the way, did you not read the whole thread? ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [August 14, 2015, 12:37am UTC](https://boards.straightdope.com/t/spark-plug-mistery/727499/23 "2015-08-14T00:37:25Z")
> [@Simple\_Mind](#): > > As one can see and as I experience myself in the past, spark plugs do fail but rarely. > > [Niterra - Der Spezialist für Zündung und Sensorik](https://www.ngk.de/en/technology-in-detail/spark-plugs/spark-plug-principles/design-of-a-spark-plug/) > > [http://www.ngk.com.au/spark-plugs/technical-information/spark-plug-analysis](http://www.ngk.com.au/spark-plugs/technical-information/spark-plug-analysis) yes, but apart from an actual manufacturing defect, they shouldn’t. and I’m not aware of a way they could be induced to hard failure by other components e.g. the ignition coil. The only problem state where I’d expect the spark plug to be “at fault” is if the wrong heat range is used, in which case fouling would still be the symptom. ---
**Author:** ![Simple\_Mind](https://avatars.discourse-cdn.com/v4/letter/s/7cd45c/32.png) [@Simple\_Mind](https://boards.straightdope.com/u/Simple_Mind)\ **Post date:** [August 15, 2015, 7:45am UTC](https://boards.straightdope.com/t/spark-plug-mistery/727499/24 "2015-08-15T07:45:52Z")
To tell the end of the story, it was the coil, it produced a to weak a spark and that fouled up the plug, even after cleaning the plug with lighter fluid and brass-brush it did hardly make a spark, a new plug would fire up and run for a while but apparently did not get hot enough to keep it clean. The solution came with a high powered after market coil for 15$, a cheap and good enough fix for me. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [August 15, 2015, 1:50pm UTC](https://boards.straightdope.com/t/spark-plug-mistery/727499/25 "2015-08-15T13:50:03Z")
Glad you got it fixed. ---
**Author:** ![Phu\_Cat](https://avatars.discourse-cdn.com/v4/letter/p/77aa72/32.png) [@Phu\_Cat](https://boards.straightdope.com/u/Phu_Cat)\ **Post date:** [August 15, 2015, 4:41pm UTC](https://boards.straightdope.com/t/spark-plug-mistery/727499/26 "2015-08-15T16:41:09Z")
Just for future reference: Just because a spark plug fires when outside the engine doesn’t mean it will fire inside the engine. The reason is the fuel and air pulled in act as insulation between the electrodes. A spark at atmospheric pressure may not happen when under compression. Phu Cat ---
**Author:** ![Simple\_Mind](https://avatars.discourse-cdn.com/v4/letter/s/7cd45c/32.png) [@Simple\_Mind](https://boards.straightdope.com/u/Simple_Mind)\ **Post date:** [August 15, 2015, 11:56pm UTC](https://boards.straightdope.com/t/spark-plug-mistery/727499/27 "2015-08-15T23:56:22Z")
> [@Phu\_Cat](#): > > Just for future reference: Just because a spark plug fires when outside the engine doesn’t mean it will fire inside the engine. The reason is the fuel and air pulled in act as insulation between the electrodes. A spark at atmospheric pressure may not happen when under compression. > > Phu Cat Correct, thanks for reminding me. [Previous page](https://boards.straightdope.com/t/spark-plug-mistery/727499.md?page=1)