This is how I was taught ot do it with the engine in the van.  Do the test when the engine is warm.. not hot or cold.

1. Remove the fuse to the fuel pump (flooding cylinder while testing is bad for test and way over-rich mixture afterwards is bad for cat-converter and valve etc)
2. Remove all spark plugs.
3. Insert compression guage. Open throttle all the way - floor acc. pedal.  Crank engine for 15-20 sec.  Take a reading.  Repeat a couple of times for each cylinder to get ave reading for the cylinder.

4. put things back.

Yau-Man Chan
87 GL

>>> "Thomas D. Hanlon" <hanran.inc@INTERNETMCI.COM> 10/06 12:47 PM >>>
Listees,
<clipped>
Can any Listee tell me a method for a DIYer ( do it yourselfer) to test
the compression in an out-of- vehicle engine?  Assume that I have a
compressor, and a compression gauge.
>>