Yes, I was blindly assuming here that the test gauge would be measuring
"in the ballpark" for accuracy, and the mechanic would be competent to
properly operate his gauge.  As Ron mentions, you do need a battery that
is good, and you must downshift to avoid lugging the engine :).

The variance between these cyls.(12 or 13%) is fine.  Widely disparate
readings (> 18 or 20%) are an indication of possible problem(s) in the
low cyl(s).  We are talking readings that are 25% lower than the low end
of the VW speced range here, so I'd have concern.

A good test of an IDI diesel engine is to start it stone cold.  If it
"lights" quickly, assuming the glows are working and all else is up to
snuff, the compression is then likely to be OK.  The combustion chamber
may only have excessive deposits and stuck rings.  A few tankfulls run
through with a quart of automatic transmission fluid added might just be
all it needs to bring the compression back.  The ATF has alot of
detergents that will clean the combustion chambers and the pump and
injectors for that matter.  I repeat the thought though that, assuming
the numbers are right for the compression of this engine, it will very
possibly, if not likely, need have to have new rings and or head work
done sooner rather than later.
-Dana-

> > The Bentley, page 15.16, gives the compression range as 406-493 psi.
> > The engine in this Vanagon needs new rings at the least...maybe head
> > work.
> > -Dana-
> >
> > > Engine compression results from inspection done two weeks ago:  #1 - 340
> > > psi, #2 310psi, #3 300, #4-300psi.  The mechanic said 300 or better is
> > > what he would want in his van.
>
> I wouldn't neccessarily go that far based ont the numbers alone.. A number
> of factors go into the readings, i.e. accuracy of gauge, how many strokes
> are measured, etc. I have taken the identical engine and tried the same test
> with a different gauge, battery, etc., and gotten very different results.
> But what didn't change dramatically between the tests was the "evenness" of
> the readings between the cylinders, and that is a very important indicator.
> 300-340 is just over a 10% variance from one cylinder to the other; not
> great but not horrible either.  I would be much more worried if the numbers
> were high (even fantastic) on some cylinders but significantly lower on
> others, i.e. 493/485/480/330.  How does it drive?  Does it lug up hills?
> Does it smoke?  Does it act like a tired engine?
>
> - Ron Salmon
>   The Bus Depot, Inc.
>   www.busdepot.com
>   (215) 234-VWVW