Black rings on my spark plugs

Mon Dec 22, 2008 1:44 pm

Hey everyone, I was using the tractor yesterday (we got a ton of snow) and noticed some discoloring on the white insulator on my plugs. I can't remember if they are Champion D16 or D21. no apparent missing. Also they are only a couple of years old. Any advice or experience? Thanks in advance.

Re: Black rings on my spark plugs

Tue Dec 23, 2008 11:06 pm

Normal for the spark plug insulators on the inside (combustion chamber side) to be discolored. The color indicates conditions within the combustion chamber. Most auto repair manuals have a section showing spark plug color and related condition(s).

Suggest visiting the library and checking out one of the auto repair manuals. The plugs could still be in excellent condition. Just need to be regaped and installed.

Black rings below the spark plug wire cap on the exterior insulators is probably grime buildup. Also normal.

Re: Black rings on my spark plugs

Wed Dec 24, 2008 3:31 pm

The discoloration is on the outside. Thank you for responding. Merry Christmas to you and all!