# craftman air compressor won't fill up



## Giles (Jan 25, 2010)

If you are referring to the pop-off valve, I think you have found the problem. I am not familar with this particular compressor but all compressors have a safety pop off valve. They are set to relieve pressure above a specified poundage. There should be no leakage in or around the valve up to the poundage setting. A UNSAFE way to check would be to plug the hole after removing the valve. CAUTION--DO NOT allow pressure to build beyond a safe pount! DO NOT run the compressor, unsupervised with this valve plugged off! 
The better solution would be to purchase a new valve.


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## vsheetz (Sep 28, 2008)

Is this something that is known to you to have worked ok, and now does not? Did it occur all of a sudden, or the pressure go down gradually over a period of time?

Does it go to 20 psi and stop - or does the motor run continually?


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## 934runner (Jan 26, 2010)

Mr vsheetz. Thks for the reply.. The compressor was bought new by me 12 years or so ago. Never had a problem untill now. The motor will run continually and the air pressure guage shows it not having more than 20psi. I let it run long enough that it should be full and then attach a air tool and there is very little pressure and doesn't last long at all.....thks


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## 934runner (Jan 26, 2010)

Giles said:


> If you are referring to the pop-off valve, I think you have found the problem. I am not familar with this particular compressor but all compressors have a safety pop off valve. They are set to relieve pressure above a specified poundage. There should be no leakage in or around the valve up to the poundage setting. A UNSAFE way to check would be to plug the hole after removing the valve. CAUTION--DO NOT allow pressure to build beyond a safe pount! DO NOT run the compressor, unsupervised with this valve plugged off!
> The better solution would be to purchase a new valve.


 SORRY MR GILES not referring to the pop-off valve.....thks


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## user1007 (Sep 23, 2009)

You have bled the tank?


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## robin303 (Dec 9, 2009)

sdsester said:


> You have bled the tank?


Here in Cen Tx I can bleed out a massive amount of water at the end of the day. You should see the crap that comes out of that thing.


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## Maintenance 6 (Feb 26, 2008)

Make sure the pop off valve has not been manually opened. Mine have rings through the stems that will allow manual bleeding of the tank pressure. Pull out for manual. Push in for auto pop off. Check the unloader valve to be sure it hasn't stuck open. If those are OK, then I would suspect a broken reed valve in the pump.


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## jlhaslip (Dec 31, 2009)

possibly bad rings or lack of oil?
might need to pull the head to check for scoring on the cylinder


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## Thurman (Feb 9, 2009)

This compressor has intake and relief valves. They are "Reed" valves, being flat, something like the "reed" on woodwind musical instrument. These valves
are notorious for getting a light rust coating on them if they sit up for even a short time. Once they get a small rust place on them, they will not seat properly. 
they will still pump some air, but when the pressure in the tank matches what faulty valve will hold back-you cannot build up any more pressure, and the head temp will rise. 1) Assure all air pressure is released, then remove the check valve again, blow air into each side. IF the air goes through the one side as it should _but not _the other side, then good-reinstall it. These do go bad on these units often. IF the check valve is good,go to: 2) again with the air relieved--remove the head and try to save the head gasket, they are hard to get. Find the "Reed" valves.They are flat metal pieces held on with one crew each, don't twist the screws off (I know). Inspect the valves to see if they are cracked, if not-- lay the valve on a sheet of fine (400+) emery cloth and polish. Do this again with a drop of oil. Clean the seating surface of the head for the valve(s) and reassemble. IF the valves are good, the check valve is good, and it still will not build up air pressure---with no known leaks--you probably have a piston ring problem. A squirt of oil directly into the cylinder is the test for this, it will do better temporarily. Hope this helps, David


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## 934runner (Jan 26, 2010)

sdsester said:


> You have bled the tank?


yes sir....I actually leave the drain valve open just slightly all the time....thank-you....and thank-you Mr robin303


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## 934runner (Jan 26, 2010)

Maintenance 6 said:


> Make sure the pop off valve has not been manually opened. Mine have rings through the stems that will allow manual bleeding of the tank pressure. Pull out for manual. Push in for auto pop off. Check the unloader valve to be sure it hasn't stuck open. If those are OK, then I would suspect a broken reed valve in the pump.


 Thank-you Mr Maintenance 6....the pop off valve is and was shut at all the check's performed....leaning toward a ring...THKS


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## 934runner (Jan 26, 2010)

jlhaslip said:


> possibly bad rings or lack of oil?
> might need to pull the head to check for scoring on the cylinder


 Thank-you Mr jlhaslip....this is a oil-less system. Going to probably start with replacing the ring & cylinder....thks


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## 934runner (Jan 26, 2010)

Thurman said:


> This compressor has intake and relief valves. They are "Reed" valves, being flat, something like the "reed" on woodwind musical instrument. These valves
> are notorious for getting a light rust coating on them if they sit up for even a short time. Once they get a small rust place on them, they will not seat properly.
> they will still pump some air, but when the pressure in the tank matches what faulty valve will hold back-you cannot build up any more pressure, and the head temp will rise. 1) Assure all air pressure is released, then remove the check valve again, blow air into each side. IF the air goes through the one side as it should _but not _the other side, then good-reinstall it. These do go bad on these units often. IF the check valve is good,go to: 2) again with the air relieved--remove the head and try to save the head gasket, they are hard to get. Find the "Reed" valves.They are flat metal pieces held on with one crew each, don't twist the screws off (I know). Inspect the valves to see if they are cracked, if not-- lay the valve on a sheet of fine (400+) emery cloth and polish. Do this again with a drop of oil. Clean the seating surface of the head for the valve(s) and reassemble. IF the valves are good, the check valve is good, and it still will not build up air pressure---with no known leaks--you probably have a piston ring problem. A squirt of oil directly into the cylinder is the test for this, it will do better temporarily. Hope this helps, David


 David. Thank-you so very much......this unit has a valve plate. I will remove the head a take a look to see if any maintance can be done on this. If not then I most likely try to install a new ring & cylinder....thks


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## Sheepdawg (Apr 7, 2010)

Well, I have a Kobalt model L-17 built by Powermate. The reed valve is broken and due to Powermate going out of business I can not get a replacement anywhere. Are there any suggestions for an alternative fix, or is my practically new air compressor useless because I can't get a $10 replacement part?

Here is a link to the manual.


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## Thurman (Feb 9, 2009)

Sheepdawg, you're not completely down and out-IMO. I have successfully repaired those reed valves by "silver-soldering" the two ends back together. The reed valves don't flex that much, but do need to move just that little bit. "Silver-soldering" is not your average solder, it needs to be done by someone who knows how. Actually, jeweler's do this type of soldering. You might try to see if you could find one who would at least try to help you. The part must be very clean and the ends very slightly beveled where they mate up. Some type of fixture to clamp them in to keep them aligned would certainly help. Good Luck, David


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## Sheepdawg (Apr 7, 2010)

Thurman, thanks for the reply. Would it still work if I just plugged/covered that one hole?


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