FREQUENCY DOMAIN ENGINE DEFECT SIGNAL ANALYSIS

A signal analyzer for detecting engine defects includes sensors (11-17) for detecting engine operating parameters such as engine speed, engine exhaust manifold pressure, engine intake manifold vacuum, blowby gas pressure in the engine crankcase, and oil pressure. Electrical signals representing the frequency and magnitude of the engine operating parameters are used to produce a frequency domain spectrum signal characteristic of the engine being tested. The frequency domain spectrum signal being tested is compared to a frequency domain spectrum signal from a normal engine thereby determining at what frequencies differences between the two signals exist, such differences being indicative of engine defects.