What is the primary purpose of a cylinder leakdown test?

The primary purpose of a cylinder leakdown test is to determine how much air is leaking past the piston rings, valves, or head gasket. This test is instrumental in diagnosing internal engine issues by applying compressed air into the cylinder when the engine is at top dead center on the compression stroke. By observing the rate of air loss, technicians can pinpoint potential problems like worn piston rings, leaking valves, or blown head gaskets.

A low leakdown percentage indicates that the engine is in good condition; conversely, high percentages suggest significant wear or damage that may require repairs. This diagnostic tool provides invaluable insight into the health of the internal components of an engine, helping in making informed repair decisions.

Options related to measuring fuel flow rate, determining engine compression, and assessing emissions control systems refer to different diagnostic tests or measurements that do not directly address air leakage within the cylinders.