When testing engine compression, what does Technician A recommend for accuracy?

Testing engine compression on a warm engine is recommended for accuracy because the components of the engine, such as the piston rings and cylinder walls, expand when heated. This expansion can improve the sealing surfaces, leading to more accurate compression readings. A warm engine typically provides a more realistic assessment of operational conditions, as the temperatures during normal engine operation are higher than those of a cold engine.

Using a pressure gauge is also vital for measuring the compression accurately; however, obtaining a reading from a warm engine is the primary factor that influences the reliability of the results. Testing only one cylinder at a time can help isolate issues but does not address the essential need for consistent thermal conditions. Testing on a cold engine may hinder the sealing effectiveness, potentially leading to lower and inaccurate compression readings.