First, I am sorry for the slow response. I have been busy with job changes.
So this is from the Clymer manual:
Compression Test
At every tune-up, check cylinder compression. Record the results and compare them at the next check. A running record will show trends in the deterioration so that corrective action can be taken before complete failure.
The results, when properly interpreted, can indicate general cylinder, piston ring and valve condition.
Note:
The valves must be properly adjusted to correctly interpret the results of this test.
1. Warm engine to normal operating temperature. Ensure the choke valve and throttle valve are completely open.
2. Remove the spark plugs as described in this chapter.
Note:
A screw-in type compression tester will be required for this procedure.
3. Connect the compression tester to one cylinder following the manufacturer's instructions.
4. Crank the engine over until there is no further rise in pressure.
5. Remove the tester and record the reading.
6. Repeat steps 3-5 for the other cylinders.
7. When interpreting the results, actual readings are not as important as the difference between readings. Standard compression pressure is specified in TABLE 8. Greater differences indicate worn or broken rings, leaky or sticky valves, blown head gasket or a combination of all.
TABLE 8:
Compression pressure (cold at sea level)
Standard 980 kPa (142 psi)
Minimum 882 kPa (128 psi)
Maximum 1,176 kPa (171 psi)
Maximum difference between cylinders 100 kPa (15 psi)
If compression reading does not differ by between cylinders by more than 10%, the rings and valves are in good condition.
If a low reading (10% or more) is obtained on one of the cylinders, it indicates valve or ring trouble. To determine which, pour about a teaspoon of engine oil through the spark plug hole onto the top of the piston. Turn the engine over once to clear some of the excess oil, then take another compression test and record the reading. If the compression returns to normal, the valves are good but the rings are defective on that cylinder. If compression does not increase, the valves require servicing. A valve could be hanging open but not burned or a piece of carbon could be on the valve seat.
Note:
If the compression is low, the engine cannot be tuned to maximum performance. The worn parts must be replaced and engine rebuilt.
That is the procedure according to my book. I hope Clymer's doesn't get mad at me for quoting their manual. Do get a manual! I know that this manual is for the Fj 1100 and Fj 1200; But should get you in the ballpark.
Hope that helps you and others with the same question.
Steve
