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Air compressor not filling tank

I have a 60 gal craftsman air compressor that will only build 92 psi. Just runs and runs, never buillding enough pressure to trigger switch. Pulled apart pump, everything looked good. Rings and cylinder walls were perfect, so i replaced gaskets and reasembled. No leaks anywere else, not sure where to go next. Very little use and only 3 years old. Help?

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  • skajaquada Jan 19, 2009

    Did replace all valves, still same. Will check for leaks again, don't think that is it. Ready to just replace punp out of frustraition. Had pump apart several times, each time replacing gaskets. Could it be rings even though they look good? Thanks for the info.

  • skajaquada Jan 21, 2009

    Did suction test on intake, no suction at all! In fact the reverse is happening. Next step? Tear down and replace vavles again? Thanks for the help.

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  • Air Tools & ... Master
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Most compressors with the problem that you are having suffer from leaking valves. As in a gasoline engine, leaking valves will lower efficiency. Valves in a compressor are in the form of reeds that seal against valve plate. Leaking reed valves or gaskets will increase the discharge air temperture. Inspect these parts with a magnifying lense. Look for evidense of wear or leaks. Also look for signs of air leaking from one cylinder to the other thru gaskets. Replace valve plate as necessary. Simple test, as your compressor is filling, check the intake for strong suction; as it neers the 92 psi mark suction will probably deminish if you have leaking valves. If suction remains strong at 92psi then you have a leak at the discharge side. Check with soapy water on all parts. Good luck

Posted on Jan 19, 2009

  • John Trevino Jan 20, 2009

    Not likely rings because all that air would be dumped into crankcase pushing out the oil from vent at dipstick. We very rarely see problems with rings/cylinder on oil bath type compressors. Oil free compressors are however known to leak past vinyl ring and cylinder at the pressure you mentioned. We pressure test reed valves/plate on special jig to 120psi. You can test discharge reeds by removing discharge tube from pump and connect air pressure hose to discharge port. Reeds should not leak into cylinders. (tank pressure should not leak past tank check valve when you remove discharge tube from head of compressor) Also you did not mention the results of blocking the intake with finger to check for suction. (try this when the unit is at 90psi). If you do not feel much suction suspect valves or air leaking thru gasket into adjacent cylinder.

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