An eccentric plug valve features off-center plug design for improved sealing, reduced wear, and efficient flow control in industrial pipelines.

I think what you are referring to is a plug used to plug a hole through compression. An example would be a casting plug, commonly called a freeze plug. It is pressed into the hole sealing it. I have heard these called Soft Plugs.

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platelets

Bad plug wire, or even bad plug it low voltage going to distributor

Also check to see if the valves are sealing properly.