Hi David -

First, this is certainly no cause for concern. Compressions are very often
more widely variable than yours in engines that run beautifully and will
pass any emissions test in the world. Many variables come into play: Carbon
deposits in combustion chambers, valve, seat, ring wear, temperature
differences between cylinders, driving and maintenance habits...

In this case I might be tempted to posit carbon buildup as a hypothesis
worth checking out. There are fiber optic tools around now that allow
inspection of the interior of combustion chambers without actually going
there - if you can find a shop that has one, it might be fun to have a peek.
Otherwise you can get a deductive clue by way of spark plug color. You could
also change the valve stem seals (if this engine has them - I don't remember
off hand), since this is the most likely source of carbon with high
compression readings.

On the other hand, it's possible that the 190 psi reading is the original
reading and the others are just the pioneers into lower compression country.
I have tested many newish FWD engines with compressions at or near 200 psi.

Coby

Valley Wagonworks
"Intimately acquainted with VW Vans since 1959"

Volkswagen Bus, Vanagon, Westfalia and Eurovan
Repair and Service Specialists

1535 Sir Francis Drake Blvd., San Anselmo, CA 94933
Voice:(415) 457-5628
Fax: (415) 457-0967
http://wagonworks.com
mailto:contact@wagonworks.com

> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM]On Behalf
> Of David Marshall
> Sent: Friday, August 13, 1999 10:00 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Fwd: Jetta engine question
>
>
> Tonight I decided to check my compression on the 1985 Jetta Carat engine
> installed in my 1984 Westfalia.  The engine was warm prior to the test and
> all spark plugs looked fine (slight brown) as they are 5000km old Bosch
> Platinums.  All plugs were removed and the throttle held wide open.  The
> engine was run for five "ka-thups" and the gauge was read.  The
> measurements were:
>
> #1 - 170
> #2 - 170
> #3 - 190
> #4 - 170
>
> According to the Bentley Manual 145-189 PSI is what these engines should
> rear with the maximum difference of 44 PSI.  I realize that I am not close
> to the 44 PSI difference limit, but why would one cylinder be way higher
> than the other three?
>
>
>
> --   David Marshall -                    - Quesnel, BC, Canada   --
> --    78 VW Rabbit, 80 VW Caddy, 84 VW Westie, 85 VW Cabriolet   --
> --       87 Audi 5000 Quattro, 88 2.0L VW Syncro Double Cab      --
> -- David's Volkswagen Home Page        http://www.volkswagen.org --
> -- Fast Forward Autobahn Sport Tuning  http://www.fastforward.ca --
> -- david@volkswagen.org (pmail) or vanagon@volkswagen.org (list) --
>