Potential high tension path in spark plug insulator

[Roland Donnell]

Installing this new Tempest UREM40E I noticed this discoloration streak inside the insulator barrel. No change in appearance after using an electrical contact cleaner on a cleaning cloth to possibly swab it out. I suspect the tooling used in the assembly process was off center. Without knowing if the deposited material is conductive I am putting it aside. I’ve got a ATS E5A High Voltage Cable Tester but I’m not sure how I would configure the connections to still be able to observe if an arc path occurs or other method. Suggestions?

 

[geezer]

That is in an area that is in relatively low electrical stress.

With the price we pay for those plugs, I would return it.

The most likely danger is that the dark color might absorb heat, creating a hot spot, and causing a crack to develop, and the warrantee is gone.

 

[Roland Donnell]

Thanks for the reply. Thought I would experiment more aggressively. Ceramic must be pretty high on the hardness scale. Took a couple of replacements but wet sanding using a dremel with the drum sander completely polished out the foreign matter.