Cleaning The Carbon Out Of Spark Plugs So They Can Be Filed Gapped And Reused
| Field | Gasoline engine maintenance |
| Went Obsolete | End of twentieth century |
| Made Obsolete By | Electronic ignitions |
| Knowledge Assumed | General mechanics |
| When useful | With an engine (car or small) that won't function and you don't have access to new spark plugs |
Spark plugs would get fouled with carbon in carbureted engines, shorting them out and inhibiting the spark. This happened frequently enough that it was not cost effective to just replace the plug; instead, it was removed, carbon was scraped out of the valley between the outer thread housing and the inner porcelain tip with a special little tool, or the plug was sandblasted inside a little cloth bag made for the purpose; the tip of the electrode was then filed down so that the edges were square again, and the plug was regapped, and replaced. Boxes containing a lot of replacement crush washers that went between the plug and the head were available, for those who felt funny about reusing the old one.
From Jollyrgr I have one plug on my truck that fouls out about once every three to six months. It takes less than ten minutes for me to pull the plug, clean it off, and put it back in. Why spend money to replace a perfectly good plug that only needs a cleaning and gapping.
On light aircraft pulling plugs and cleaning them is MUCH cheaper as the plugs cost about $30 to $40 EACH! (And you can clean these by using the mixture setting while doing a runup.)
