In reply to a message from QuangXJ40 sent Fri 24 Mar 2006:
You’ve got the basics. What I do is to remove all of the spark
plugs for the test (engine spins freely and faster that way). I
haven’t bothered with coil wires or fuel relay.
With all of the spark plugs out, you can easily tell from the sound
when the cylinder being tested is on its compression stroke. I
stop cranking after 6 compressions and write down the pressure,
then move to the next cylinder.
While you’re under the hood (bonnet), check the intake manifold
bolts for tightness (10 and 13 mm wrenches) and thoroughly inspect
any hose that connects to the intake manifold for cracks. Also
inspect the injectors for leaking fuel.
If you have one cylinder with significantly lower pressure than the
others, it’s most likely a burned exhaust valve.
You can also do a ‘wet’ compression test to assess the performance
of the piston rings after you do the ‘dry’ test. Squirt some motor
oil into the spark plug holes then run a compression test again.
Squirt the oil in just before you attach the gauge. Crank the
engine for the same number of compressions as you did for the ‘dry’
test. The oil will temporarily seal any imperfections in the rings
during the ‘wet’ test. Comparing the ‘wet’ and ‘dry’ numbers will
give an indication of how ‘bad’ the rings are.–
The original message included these comments:
Remove each of the spark plug, hook the compression test up, and
crank the engine a few times. Record the reading on paper. Repeat
the proces for other cylinders. I suppose cylinders are
independent of each other so I don’t have to put back spark plug #1
once I move one to #2.
Am I accurate? Please provide me any tips you might have.
–
Pete 70 XKE (193K) 88 XJ6 (233K) 88 XJ6 (217K) 60 Mini
Severna park, Maryland, United States
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