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Wet and dry Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Thu, 18 Sep 2008 06:17:59
In Reply to: Compression test readout low, piston ring?, Kremlins, Thu, 18 Sep 2008 00:58:32 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The numbers seem a little low, but there is a lot that goes into a compression test.
The fact that the numbers are all quite close together is a very good sign.
Two big factors on compression tests are technique and battery condition. You should turn the engine over enough times that the gauge stops going up; typically 3-5 turns. Remember, you only get one compression stroke every two rotations, so if you go by turns, you can shortchange a cylinder. It's good when the value jumps up quickly on the first compression stroke, and then increases only slightly after that.
Battery voltage determines how fast the engine turns, and that has an impact on compression. Faster gives a higher number. Are you doing the test with all spark plugs out? It'll turn faster that way.
Also - calibrated your gauge? I'll bet not.
The fact that the values are close together is good. If you want to check the rings, do a wet test. After doing a dry test, squirt in a teaspoon or two of motor oil into a cylinder, turn it over a couple/three times, then retest that cylinder.
If you see a big jump in compression 'wet' - say 20 psi jump - that implies the rings are weak. If you see minimal increase, then the rings are OK.
If you drive downhill and let off the gas, and you see burning oil from the exhaust, suspect the valve seals. No burning oil, and the valve seals are probably fine.
Bottom line - your engine may be just fine. Sorry.
posted by 192.249....
, Thu, 18 Sep 2008 06:17:59 <-- Viewing This Message, Thu, 18 Sep 2008 10:32:56
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