I know my compression tester came over with Columbus, but I've replaced the o-ring and shraeder valve and I still can get any result I want practically by cranking more or less. It was interesting to read you seem to get similar results.

>...when you activate the switch, the starter engages, but it's ONLY the starter.

Careful on the k-jet cars with ballast resistors -- the starter's ballast contact supplies voltage to the ignition coil without benefit of the ignition switch, so be mindful of where those high tension leads are.
--
Art Benstein near Baltimore