Compression Check: Tools and Equipment
CYLINDER LEAKAGE TESTER
Standard compression gauges cannot detect small leaks which may still affect performance of modern engines using lean fuel/air mixtures. A cylinder leakage tester is a more reliable way to pinpoint improper valve seating and other mechanical problems which may cause slight leaks.
Normal shop air pressure is regulated at the left side gauge - the right side gauge reads pressure in the combustion chamber which is connected by an adapter to the spark plug hole. The passage connecting the two gauges is so narrow that the right side gauge will read lower than the left one if there is any cylinder leakage.