[Vwdiesel] Analyzing compression numbers - oil in injector hole?

[Will Taygan]

I compression tested the 91 ecodiesel a month ago and got
450-480-450-400.  (the 94 TD was 450-500 on all 4!)

It starts well when cold, starts well when hot, but there's a zone when
it's just warm and the glow plugs don't come on that it cranks for a few
seconds before it catches.  Engine? Pump? Glow Sensor?  The afterglow is
7 seconds, so I just double-glow the 7 second period (no light, just
current) and things usually improve.

I found a good teaspoon of oil in the #4 injector hole (lowest
compression cylinder) when I pulled it.  I've never seen that before.

There is some trace oil in the coolant overflow.  Looks like it had a
blown headgasket that someone repaired and now there's just a film on
the plastic.  Maybe a few pencil-dot sized specks of oil floating in
there.

I'm not too worried about it, just curious.  Ideas? Theories?

Will.