Compressor Pressure Does Not Build Up Over 25PSI, No Leaks

Reply

  #1  
Old 08-22-11, 03:32 PM
P
Member
Thread Starter
Join Date: Feb 2008
Location: USA
Posts: 16
Received 0 Votes on 0 Posts
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.
 
  #2  
Old 08-22-11, 03:51 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,965
Received 6 Votes on 6 Posts
The only thing I can think of is a bad reed valve. Fairly easy to replace. Pull the head off the compressor and see if that isn't the case.
 
  #3  
Old 08-22-11, 07:01 PM
P
Member
Thread Starter
Join Date: Feb 2008
Location: USA
Posts: 16
Received 0 Votes on 0 Posts
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  
Old 08-23-11, 04:34 AM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,965
Received 6 Votes on 6 Posts
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.
 
  #5  
Old 08-23-11, 09:20 AM
P
Member
Thread Starter
Join Date: Feb 2008
Location: USA
Posts: 16
Received 0 Votes on 0 Posts
Are the reeds just supposed to be laying in their respective cutouts in the valve plates? If so, that's where I found them.
 
  #6  
Old 08-23-11, 05:11 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,965
Received 6 Votes on 6 Posts
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  
Old 08-29-11, 09:24 AM
P
Member
Thread Starter
Join Date: Feb 2008
Location: USA
Posts: 16
Received 0 Votes on 0 Posts
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.....
 
  #8  
Old 08-30-11, 08:45 AM
M
Member
Join Date: Oct 2003
Location: PA, USA
Posts: 748
Received 0 Votes on 0 Posts
Did you check out the head gasket while you were in there? Especially the thin section in the middle that separates the intake and exhaust valves.
 
  #9  
Old 08-30-11, 09:37 AM
P
Member
Thread Starter
Join Date: Feb 2008
Location: USA
Posts: 16
Received 0 Votes on 0 Posts
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  
Old 08-30-11, 09:42 AM
M
Forum Topic Moderator
Join Date: Mar 2005
Location: USA - N.E.Tn
Posts: 47,845
Received 361 Votes on 318 Posts
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  
Old 09-01-11, 10:16 AM
P
Member
Thread Starter
Join Date: Feb 2008
Location: USA
Posts: 16
Received 0 Votes on 0 Posts
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  
Old 09-01-11, 10:28 AM
M
Forum Topic Moderator
Join Date: Mar 2005
Location: USA - N.E.Tn
Posts: 47,845
Received 361 Votes on 318 Posts
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  
Old 09-01-11, 11:03 AM
F
Member
Join Date: Mar 2006
Location: Wet side of Washington state.
Posts: 18,495
Received 36 Votes on 28 Posts
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  
Old 09-01-11, 11:34 AM
M
Member
Join Date: Oct 2003
Location: PA, USA
Posts: 748
Received 0 Votes on 0 Posts
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  
Old 09-02-11, 07:45 PM
P
Member
Thread Starter
Join Date: Feb 2008
Location: USA
Posts: 16
Received 0 Votes on 0 Posts
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  
Old 09-08-11, 05:29 PM
P
Member
Thread Starter
Join Date: Feb 2008
Location: USA
Posts: 16
Received 0 Votes on 0 Posts
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  
Old 09-08-11, 07:18 PM
M
Member
Join Date: Oct 2003
Location: PA, USA
Posts: 748
Received 0 Votes on 0 Posts
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.
 
  #18  
Old 09-13-11, 02:09 PM
P
Member
Thread Starter
Join Date: Feb 2008
Location: USA
Posts: 16
Received 0 Votes on 0 Posts
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.
 

Last edited by patmac; 09-13-11 at 03:20 PM. Reason: More info
  #19  
Old 03-31-13, 12:14 PM
S
Member
Join Date: Mar 2013
Location: United States
Posts: 1
Received 0 Votes on 0 Posts
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!:
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: