neil N wrote:
> Used w/o adaptor (engine cold) I got:
>
> 150 150 150 Then......
>
> 50 on # 3. :((
>

The first thing that comes to mind, is that if that cylinder really was
50, the van would run like total crap. You could start it, pull that
plug wire, and it would make no difference at all. That is an easy check.

You want to put teaspoon of oil into the cylinder, and test it again. If
the reading comes up, its likely rings. If not, valves, and then I would
try backing off the lifter adjustments on that cylinder.

It may come down to needing a leak down test, but so far, you have seen
readings that are really all over the place, so I would  work on
consistency, before I even  pulled a valve cover, or did anything major.

Are you blocking the throttle open when you test, and are you being as
consistent as you can, with the number of strokes per test?

Just don't tear anything apart, until there are fairly consistent
numbers. Just when you think things are somewhat falling apart, they
really can unravel quickly into a poor diagnosis :-)

John