In a message dated 1/26/05 12:49:17 AM, xtabe@YAHOO.COM writes:

<< What am I missing here? >>

Everything.  A leak down tester applies a regulated pressure to the cylinder
under test and the resulting pressure in the cylinder is read as a percentage
of the regulated pressure.  To keep things simple, the regulated pressure is
usually 100 PSI making the percentage leakage merely the difference between the
two pressures.  For a leak down test to be valid, the valves must be kept
fully closed.  As matter of safety, the piston in the subject cylinder must be at
bottom dead center so that the application of the air does not rotate the
crank.

George