After a compression test reveals readings of 140, 135, 135, and 40 psi on a 4-cylinder engine, which technician is correct regarding the potential causes?

In this scenario, a significant discrepancy in compression test readings indicates that there is likely an issue with the engine's components. The first three cylinders show relatively consistent compression readings (140, 135, 135 psi), while the fourth cylinder has a much lower reading of only 40 psi. This suggests that there could be a problem with that specific cylinder, potentially caused by several factors such as worn piston rings, a blown head gasket, or a valve issue.

Given the nature of compression testing, any cylinder that shows a reading significantly lower than the others often points towards mechanical failure or loss of sealing within that cylinder.

The technician who pointed out this inconsistency is correct because it highlights a clear area of concern that would require further investigation, such as a leak-down test, to pinpoint the exact cause of the low compression. Understanding these symptoms is critical for diagnosing engine problems, as it directly pertains to the engine's ability to generate power and maintain efficiency.

This focus on the condition of the individual cylinder in question illustrates the importance of analyzing compression readings and correlating them with potential mechanical issues within the engine. Recognition of such patterns can lead to accurate diagnoses and effective repairs.