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Compression Test - Interpreting Compression Readings

WARNING: This page is about a different car, the 2012 Ford Pickup, 2012 Ford F550 Super Duty, and 2012 Ford F450 Super Duty. However, it is still accessible from the selected car via links, so may be relevant.
  1. If compression improves considerably, piston rings are faulty.
  2. If compression does not improve, valves are sticking or seating incorrectly.
  3. If 2 adjacent cylinders indicate low compression pressures and squirting oil on each piston does not increase compression, the head gasket may be leaking between cylinders. Engine oil or coolant in cylinders could result from this condition.

    Use the Compression Pressure Limit Chart when checking cylinder compression so that the lowest reading is within 75% of the highest reading.

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