Join Date: Dec 1999
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Re: Compression Testing: Correct Method?
disable ignition first!
mark the wires, remove all plugs.
get a notepad, screw guage into Hole#1 have someone crank engine over several times, record the highest number on guage ( guage should hold peak reading).
do all 6 or all 8 whatever your working with.
if any are low ( Lower than the rest by more than 10% or so) then ad oil to those cylinders, a squirt or a teaspoon full, reattatch compguage to plug hole and retest, if the low cylinders come up with teh addition of oil, then its a ring seal problem.
if the readings dont come up with oil, then its a valve problem, either burnt edge or, valve train not opening it ( worn cam lobe/broken rocker arm/bent pushrod)
you can find the weakest seal in your cylinder by bring whichever cylind you wish to test to TDC, put teh rig in NUETRAL, engage parking brakem, choke the wheels.
screw the compression guage hose into the plug hole, turn your air compressor to about 20PSI, attatch IT to teh hose instead of the guage and slowly increase pressure until you hear the hiss, you can easily hear exhaust, intake or crankcase.
poor mans leakdown test, not as accurate, but has told me alot of things in the past.