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compression test

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Old Oct 16, 2009 | 12:00 PM
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Default compression test
im trying to do a compression test on my 1990 f250 460 and i dont know the psi. does anybody know the psi.
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Old Oct 16, 2009 | 02:26 PM
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"Lowest cylinder must be at least 75% of highest cylinder"- straight from the manual.
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Old Oct 16, 2009 | 04:08 PM
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whats 75% of 145
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Old Oct 16, 2009 | 05:07 PM
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Originally Posted by 91351
whats 75% of 145
~109
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Old Oct 16, 2009 | 05:45 PM
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thanks guys
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Old Oct 16, 2009 | 07:16 PM
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Put your finger on the hole, if the compression blows your finger back, its fine. If you finger doesnt move, the cylinder is low.
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Old Oct 18, 2009 | 10:04 PM
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ok 5 cylinders 145 psi 1-150psi 1-140 psi 1-90 psi
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Old Oct 18, 2009 | 10:44 PM
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that one doing 90psi aint good...did you squirt a little oil in the hole and re-try it?
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Old Oct 18, 2009 | 10:46 PM
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no but the sparkplug was covered in oil and the truck burns it like candy so theres oil gettin in there
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Old Oct 19, 2009 | 03:16 AM
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If the oil brings up the compression then it's bad rings. If the oil does nothing then it's a stuck or worn valve or seat.
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