If a cylinder compression test yields a low reading, how can a technician perform a 'wet' compression test to isolate the cause between worn piston rings and leaking valves?

1. Pour a small amount of clean engine oil into the spark plug hole and retest; if compression rises, the rings are worn; if it remains low, the valves or head gasket are leaking.
2. Pour water into the combustion chamber and check if it bubbles out through the exhaust pipe during cranking.
3. Retest compression while spraying soapy water around the outside cylinder head gasket area to look for bubbles.
4. Pour fuel stabilizer into the fuel tank and crank the engine with the throttle closed to see if the reading changes.