Something makes no sense on this problem. Short of a piston that didn't go up and down, the "hole" that allowed cylinder pressure to escape to atmosphere would have to be almost as large as the intake or exhaust valve opening...that's big!
A simple blown head gasket or stuck or broken ring would still allow the cylinder to build 'some pressure'.
If either valve was hung completely open, you would have other real obvious symptoms, and if the piston weren't going up and down, well...suffice it to say you would probably know that too.
Zero cylinder pressure on a compression test would have to have additional telltale symptoms....I think!
I would question the test procedure on that cylinder.
Stuart
