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Old 10-18-2012, 02:27 PM
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rover67 rover67 is offline
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Join Date: Nov 2007
Location: Boulder, Co
Posts: 6,804

First, be careful pressurizing cylinders....

I have had a wrench on the crankshaft almost kick my ass when I pressurized a cylinder at TDC and it slung the thing at me. Make sure the motor is locked somehow. I usually find TDC on a cylinder by putting the hose in the spark plug hole and holding my thumb on it. Rotate the crank till it spits air out under pressure, then stops. Thats TDC on the compression stroke. you can stick a wire in the spark plug hole to see where the piston is and get it right at TDC. Then I lock the motor, hook it up to air and go for it. Sometimes it is nice to purposely let it go just beyond or before TDC so you know which way the motor is going to kick and can be ready for it with a wrench jammed against a frame rail or something.

When you pressurize the cylinders you shouldn't really hear any leakage if it is in pretty good shape. usually you only hear a ton of leakage when there is a problem. Either way look at the difference between the line pressure and the cylinder pressure to figure your leak down percentage.

Back to the compression test... your numbers are all very even. Surprisingly even actually... They did come up a bit with oil, which is almost always the case even on a healthy motor. Not knowing what that motor typically pumps up to (compression ratio is a big factor) I'd say it looks like it is in good shape but slightly worn maybe. Probably rings getting tired.

I'll go check out the mud thread in a bit.
Marco Capote
85 FJ60
82 FJ40
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