[Tommy]

A Google search will tell you much more than I can, but here are the basics. When you engage the starter, the gauge needle moves up as the pressure in the cylinder rises as the piston moves. Most gauges hold the needle at its highest reading so you can see it easily after you release the starter. A reset button lets you prepare the gauge for the next test.

This gauge measures only static compression. Dynamic compression occurs when the engine is running. .... Max PSI is either the highest pressure the gauge can read, or it might refer to the highest reading on the needle after each test. ... Again Google is your friend and it might even have the answer in Spanish.