Interpreting Compression Readings

AllData Editors Note - Ford does not provide a cranking pressure specification, only an acceptable range.

1. If compression improves considerably, piston rings require service.
2. If compression does not improve, valves are sticking or seating improperly.
3. If two adjacent cylinders indicate low compression pressures and squirting oil on piston does not increase compression, the head gasket may be leaking between cylinders. Engine oil and/or coolant in the cylinders could result from this condition.

Compression Pressure Limit Chart.:

Use the Compression Pressure Limit Chart when comparing cylinder compression readings to determine if the lowest reading is within 75 percent of the highest reading.