Question

How even should the cranking compression be between the lowest and highest cylinder readings on an engine without mechanical problems

Answer 1

It should be within 10%

Step-by-step explanation:

Cranking compression is simply the pressure that builds up inside cylinders when the valves are closed and the piston then moves up the bores to lead to compression of the mixture.

Cranking compression is normally measured in pounds per square inch (PSI).

When checking cranking compression, we should be looking for signs of replication between cylinders. It means that each cylinder should build pressure within about 5 percent of the others under the same number of starter revolutions. Thus, the variation between the highest and lowest readings should not be more than 10%