RE:<ALL>E28 Compression Check

[Rodney Moore <m6bigdog@xxxxxxxx>]

Your procedure in doing a compression check will cause inconsistent 
results.
Using proper preparation and procedure during a compression check yields 
better results:
1.  Clean top of engine before removing valve cover and blow dirt out of 
plug wells.
2.  Adjust valve clearance at specification engine temp.
3.  Loosened spark plugs several turns and then retighten. (this keeps 
flakes of carbon from getting stuck on the valve seats when plugs are 
removed for compression test)
4.  Run engine until near operating temp.
5.  Remove all plugs
6.  Block or wire throttle linkage to open butterfly. (full throttle is not 
necessary but having the throttle off idle is)
7.  On each cylinder;  read compression on first full compression stroke 
and count engine strokes to obtain final compression value (first full 
stroke will produce approximately 80% of a final compression value, use a 
fixed number of strokes for each cylinder, 10 strokes max).
8.  Record compression on first full stroke and final compression value for 
each cylinder.
9.  Compare values, consistency with in 10% for all readings is more 
important than the actual value.

Cylinder leak down testing is also an excellent diagnostic test for piston 
ring and valve condition.

- -----
Rodney Moore
e-mail: m6bigdog@domain.elided

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