Which condition is NOT required for a proper compression test?

A proper compression test is designed to measure the ability of an engine cylinder to hold pressure. For this test to yield accurate and reliable results, certain conditions must be met.

Having all spark plugs removed is a common practice during a compression test, as it allows the engine to turn over more freely and reduces stress on the starter motor. This facilitates a more accurate measurement of the cylinder pressure because the engine can spin without unnecessary resistance.

In contrast, having the battery fully charged ensures that the starter motor is able to crank the engine effectively. If the battery is weak, the engine may not turn over fast enough, leading to lower and inconsistent compression readings.

Running the engine at operating temperature is crucial as it allows the components, such as the pistons, rings, and cylinder walls, to expand to their normal working dimensions. This expansion can significantly affect the compression readings if the engine is cold.

Ensuring that the valves are properly adjusted is also important because maladjusted valves can lead to incorrect compression readings. If the valves do not close fully, it results in a loss of pressure that can misrepresent the actual health of the engine's internal components.

Thus, the requirement that is not necessary for a proper compression test is having all spark plugs removed; the