Originally Posted by
simonwright
Yes. Done properly, the test can identify pressure leaks occurring through the intake or exhaust valves, by the rings, or through head or barrel cracks. The procedure involves applying a known pressure into the cylinder bore with the piston at Top Dead Center (TDC) and measuring the reduced pressure in the combustion chamber due to leakage.
For TCM engines, the pressure is generally input through the top spark plug port and the pressure is measured with the differential compression tester.
Always useful to know when the topic is, erm, pressure testing fire extinguishers....