Engine CompressionAtmospheric pressure at sea level is approximately 14.7 psi.A 9:1 compression ratio cylinder is compressing the air and fuel mixture to about 132 psi at sea level (9x14.7=132.3 ...

With a simple diesel engine compression test, it is possible to spot compression problems before they get worse. Here’s information on these tests and how to decide if it is time to perform one.