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SKU 39224 Page 5
10. On a low compression engine, if the compression increases after the oil has
been added, worn rings are definitely indicated. If the compression doesn’t
increase significantly, the leakage is occuring at the valves or head gasket (or
cracked head).
11. If compression is low in two adjacent cylinders, it is
likely that the cylinder head between them is leaking.
If coolant is found in the combustion chambers or
crankcase, this possibility is confirmed.
12. If the compression on one cylinder is 20% or so lower
than the others, and the engine has a rough idle, it
is likely that the valve is stuck or the camshaft has
a worn lobe.
13. If the compression is unusually high compared to
the engine specifications, it is likely that the cylinders
are carbonized. A qualified mechanic should remove
the engine head and remove the carbon.
14. If the compression varies greatly (over 15%) from
the highest compression cylinder to the lowest, or
the average compression is significantly lower than
the specification, the engine should be looked at by
a professional for a leak-down test or other service
to identify and repair the problem.
Maintenance
Very little maintenance of this tool is required. Keep this tool clean and free from dirt,
grease or grit. Store it in its case when not in use. Periodically check the threads for
damage. Release the pressure from the gauge before storing.
Note: Replacement parts are not available.
Pressure
Release
Valve
Quick
Release
Chuck
7. Crank the engine over several compression strokes and watch the gauge. On a
healthy engine, the compression will build up quickly. Low compression on the
first stroke followed by a slow build up of pressure indicates worn piston rings.
Low compression which does not build up indicates leaking valves, a blown
head gasket or cracked head. Carbon deposits on the valves can also cause
low pressure. Record the highest compression obtained.
8. Repeat this procedure for each of the remaining cylinders and record the results.
9. On a low compression engine, add approx. 1/4 oz. motor oil to each cylinder
through the spark plug hole and repeat the procedure.