Compressor Pressure Does Not Build Up Over 25PSI, No Leaks
#1
08-22-11, 03:32 PM
Compressor Pressure Does Not Build Up Over 25PSI, No Leaks
Hi,
This is on a Craftsman 3 Gallon, 1 HP Oil Lubed air compressor, 125PSImax.
It will build pressure to around 25-30 PSI, and that's it. When I shut it off, the pressure remains there, does not diminish at all.
I realize these have a pretty low duty cycle, and I just recently finished using this for a floor nailer on a 24 x 24 room, but it worked OK after that, until now.
Any quick ideas where to start, before I start pulling the whole thing apart?
Thanks for your time.
This is on a Craftsman 3 Gallon, 1 HP Oil Lubed air compressor, 125PSImax.
It will build pressure to around 25-30 PSI, and that's it. When I shut it off, the pressure remains there, does not diminish at all.
I realize these have a pretty low duty cycle, and I just recently finished using this for a floor nailer on a 24 x 24 room, but it worked OK after that, until now.
Any quick ideas where to start, before I start pulling the whole thing apart?
Thanks for your time.
#3
08-22-11, 07:01 PM
Thanks. I see the two valve plates, two fabric gaskets, a single metal gasket, and what I'm guessing are the two "reeds". What should I be looking for? There are small blue fabric gasket pieces all around, but the gaskets themselves don't show any cuts or cracks. Is the reed valve the two reeds and the plates that they go in? Thanks
#4
08-23-11, 04:34 AM
Yes, how are they seated? If their seat is not complete they will not build up pressure. It won't leak pressue down, but just won't build it up. Sort of like running a compression release on a motorcycle. When the compressor was running, did you feel air coming from the intake? Generally that is a good indicator of reed failure, too. Since you are down to it, you can change the reeds and build it back up. At least you won't have a great deal of money invested. Getting deeper, you could have a compression ring on the compressor failing. Now you're getting into a little more teardown and rebuild, but doable.
#6
08-23-11, 05:11 PM
Yes, they will lay flat in the recess and bend as air is forced from the compressor head to the tank, and return to the flat position when pressure backs up against them.
#7
08-29-11, 09:24 AM
I checked and cleaned the valve body and reeds, with no change. I removed the pressure relief valve and the regulator and plugged them, with no change. Are the next steps more costly?? 
This wasn't a real big expenditure, so I would not mind getting a new one, but I would like to see if I can find the problem. Thanks again for your time.....
This wasn't a real big expenditure, so I would not mind getting a new one, but I would like to see if I can find the problem. Thanks again for your time.....
#9
08-30-11, 09:37 AM
Yes. There's no scoring or bends in it. Since my last post I found a couple of loose fittings and changed the oil with no difference. I just removed the cylinder and all appears well there ( not my area of expertise at all ). The cylinder walls are smooth with no scoring. The piston appears OK. The only thing I'm alittle confused about ( besides how to get the pistion back into the cylinder housing ) is about the rings. The print shows two compression rings and a scrapper ring. Am I correct when I say the two compression rings are split? The third ring is split as well, although that's not clear on the print. Thanks for your time.
#10
08-30-11, 09:42 AM
The rings are split so they can be installed. They should be oriented so none of the gaps are in the same line. You use a piston ring compressor to tighten them up and slip them into the cylinder.
#11
09-01-11, 10:16 AM
Thanks, but I'm having trouble finding ring compressors small enough. The diameter of the piston is 1 3/8". There is one around for 1 1/2", not sure if that would work or not.
#12
09-01-11, 10:28 AM
If I remember correctly, they are adjustable for different sizes..... but you need one that is adjustable for your size piston. I've never needed one for something that small.
#13
09-01-11, 11:03 AM
Cut a sheet of metal from a tin can (get rid of the rolled edge) and wrap it around the piston overlapping the ends of the metal. Use a worm-gear hose clamp to tighten the sheet metal enough to compress the rings. Be sure to first liberally oil the piston and rings.
#14
09-01-11, 11:34 AM
Before you invest in or make a ring compressor, see if the bottom of the cylinder is taper cut to accomodate installation without any tools. If it is, just squeeze the ring with your fingers and push the piston into the cylinder.
#15
09-02-11, 07:45 PM
I just had time to check the bottom of the cylinder, and yes, it does have a chamfer on it. No time right now to re-install..will get back here later on...Thanks.
#16
09-08-11, 05:29 PM
OK, thanks Markiz37, I just re-assembled the piston into the cylinder. While I had the connecting rod out I checked in the motor housing all looks well. Any ideas ( after checking what I have done...it's been awhile..sorry )? I see there is a connection that tees from where the air goes into the tank. It's a small diameter copper tube that goes to the On/Off switch. Now the pressure gage that's on the switch housing is the only thing I didn't blank off. I'm thinking of trying to cap off that small tubing to see if there's an issue there.....any other ideas? Thanks again for your time.
#17
09-08-11, 07:18 PM
copper tubing
That tubing is the unloader line. It is possible that the needle valve on the other end of that tube (inside the switch) is leaking. Cap that off, it's probably easier to do it at the tee, with a pipe plug. Then see if you can pump beyond the 25#. If all goes well, replace the switch with a similar model and reconnect the tubing.
Also, in that tee, there is a check valve connected to the pump line. It keeps pressurized air in the tank. Check it out if you haven't already. They gum up, warp or corrode sometimes and let air back out into the head. Be careful, don't wrench on a pressurized tank. Good luck.
Also, in that tee, there is a check valve connected to the pump line. It keeps pressurized air in the tank. Check it out if you haven't already. They gum up, warp or corrode sometimes and let air back out into the head. Be careful, don't wrench on a pressurized tank. Good luck.
#18
09-13-11, 02:09 PM
Thanks. I capped off the unloader line, with no change. Is the check valve in the tee at the junction where the supply line comes out of the cylinder head and the unloader meet?
Ok, figured that out...but before I go further...need to tell you the pressure was getting up to 40 psi before I opened the check valve to check it. After I put it back to gether it was only getting up to 30 psi, still more than before.
Could this just be a seal/gasket problem? Early on I said I found blue pieces of gasket fabric all in and around the valve body. I never saw any cuts or scrapes on any of the sealing surfaces, metal or fabric gaskets/seals.
Ok, figured that out...but before I go further...need to tell you the pressure was getting up to 40 psi before I opened the check valve to check it. After I put it back to gether it was only getting up to 30 psi, still more than before.
Could this just be a seal/gasket problem? Early on I said I found blue pieces of gasket fabric all in and around the valve body. I never saw any cuts or scrapes on any of the sealing surfaces, metal or fabric gaskets/seals.
Last edited by patmac; 09-13-11 at 03:20 PM. Reason: More info
#19
03-31-13, 12:14 PM
Check that reed valve gasket!!!
Well, I just fixed mine. I swear I spent money needlessly. New regulator,lines etc. I thought that I checked all of the gaskets, but come to find out, it was the reed valve gasket just above the piston head. Der...... Made my own, works like new again. (It should!) lol Happy Camper now! I was on a mission!
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