Compression Test - Interpreting Compression Readings

Compression Test - Interpreting Compression Readings

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