My guess is that it is for air cooled buses that have engine tin covering
the cylinders and spark.  The rubber ring helps keep air flow around the
motor and not from escaping out the spark plug access holes - the rings
should be removable I believe.  Nothing more fun than dropping a spark plug
and fishing it out from underneath the tin.

Bruce

On Thu, Jun 10, 2021 at 8:22 AM Dan N <dn92610@gmail.com> wrote:

> hi all,
>
> Recently I did a tune up on my 1988 Carat 2.1 WBX I noticed that the spark
> plugs caps have a rubber ring on them. I looked at my son's 1989 GL
> the spark plugs caps don't have the rubber ring. On both vans the spark
> plugs wires were replaced some years ago (Bosch brand I guess)... so the
> questions..
>
> - why do some spark plugs wires/caps have the rubber ring and some don't?
>
> - I guess the spark plugs rubber rings are there to prevent dirt going into
> the cavity and around the spark plugs caps. Is it essential (or must have)
> to have a rubber ring or is it optional?
>
> thanks
>
> dan
>