Issue with air compressor

[Mhardee86]

I recently had to rethread and replace the drain plug in a 60gal air compressor.
I also noticed that the psi will not get above 40-45 lbs. I let it run for 30min but still wouldn't get above 45lbs.

Can anyone help me out? It's been awhile since I was able to get this compressor running again and I would hate to buy a new one since this one was working before.

 

[The Cobbler]

what kind of compressor?
first thing I would do is check everything for leaks .
for the feed line to the tank you will need to do that with the compressor running . check for leaks at the head too . .
also make sure the unloader is not leaking.

 

[Mhardee86]

I don't hear any leaks. It's a u.s. general 3848.
Unloader?

 

[The Cobbler]

you will need to run the compressor to check for leaks from the compressor head to the tank . that part has no pressure in it when the unit is not building pressure .you won;t hear a leak there while it's running . the unloader is the valve that lets pressure off the head when it stops so it can restart without pressure on it

 

[Citation]

I would guess it's a broken valve in the head.

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(See part 0001)
A bad check valve won't stop it from building pressure. Instead it would leak after the pump turns off. Failure to build while running is typically a pump problem or a gross leak.

 

[Mhardee86]

I've checked again and wasn't able to feel or see a leak. I'm guessing I'll need a new pump assembly from the above link?

 

[Citation]

Have you pulled the head yet? Not the whole pump, just the head off the cylinders. I'm guessing a broken valve which is relatively cheap. $40 here - do verify I've picked the right part!

B2800 / B3800 Air Compressor Pump Valve Plate Kit #05C181

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You won't feel the leak since it's inside of the head. It just won't pull as much air.

 

[vwpieces]

I don't hear any leaks. It's a u.s. general 3848.
Unloader?

HF don't even list US General compressors anymore on the website. Odd, didn't know they discontinued them. The 3848 not shown on the site.

Can you hear the motor CLICK and go to a higher speed? If not, could be a bad Capacitor or RUN contact plate.
My CH 60gal had this issue and would only go to 35ish PSI. But as it turns out there was a mud dobber nest inside the motor, not allowing the centrifugal contact to move into position. No "second gear" for the high speed Run mode.

 

[Mhardee86]

I don't hear any clicks or odd noises from the motor or pump

 

[vwpieces]

I don't hear any clicks or odd noises from the motor or pump

I would test the motor capacitors. A good DMM will have this function. Rating should be on the Cap. Many vids out there to help if needed.
Caps are cheap, but sometimes finding one in the dimensions needed is difficult.

 

[Citation]

I would test the motor capacitors. A good DMM will have this function. Rating should be on the Cap. Many vids out there to help if needed.
Caps are cheap, but sometimes finding one in the dimensions needed is difficult.

If the motor starts and runs but pressure doesn't build the issue is probably not the motor. Bad valves in the pump would explain building to a low pressure then continuously running as the tank pressure never gets above the shut off point. It also wouldn't make noise once the pump is turned off.

 

[vwpieces]

If the motor starts and runs but pressure doesn't build the issue is probably not the motor. Bad valves in the pump would explain building to a low pressure then continuously running as the tank pressure never gets above the shut off point. It also wouldn't make noise once the pump is turned off.

I get it but testing the caps and even confirming Motor RPM can be done first, before tearing the pump apart.
Here is a pic of a broken HP valve in my Quincy QT-5. Don't mind the extra hole at the broken end. It was a test to see if I could punch a hole in the spring steel before buying the material to make my own valve. And Yes, I did make my own valve and it is running strong almost exactly a year later.
Anyway my point is that even with that broken valve the pump did run up to 175psi and turn off. 0-175psi run time to fill the 80gal tank was about 10min. Most people would not even thing there was something wrong... But I knew the runtime should be in the 6ish min range with the pumps output.

 

[Citation]

You are

I get it but testing the caps and even confirming Motor RPM can be done first, before tearing the pump apart.
Here is a pic of a broken HP valve in my Quincy QT-5. Don't mind the extra hole at the broken end. It was a test to see if I could punch a hole in the spring steel before buying the material to make my own valve. And Yes, I did make my own valve and it is running strong almost exactly a year later.
Anyway my point is that even with that broken valve the pump did run up to 175psi and turn off. 0-175psi run time to fill the 80gal tank was about 10min. Most people would not even thing there was something wrong... But I knew the runtime should be in the 6ish min range with the pumps output.

You are right, checking the motor is cheap and easy. They said, broken valves seem most likely to me.

 

[redmondjp]

I would also check for a loose/slipping belt. Any air leak large enough to hold the pressure down to that level should be easily discoverable. I'm thinking broken reed valve as well.

 

[Mhardee86]

Took the head off and these are the values

 

[vwpieces]

Hmmm... Gasket failure. Sure could have been a lot worse.
You will need to flatten the head best you can. But definitely do-able with a good piece of glass and sandpaper. Gasket set should also be reasonably priced.

 

[vwpieces]

If you are able to find a recommended torque value for the head bolts and torque sequence, double check them after a Few heat cycles and perhaps a couple times a year after.

 

[Citation]

From my link above the head gasket is $20 in a kit. It looks like the right part but again, verify the numbers

 

[vwpieces]

From my link above the head gasket is $20 in a kit. It looks like the right part but again, verify the numbers

didn't check the link till now, but for $40 I would do the kit with valve plate.
Also assuming it is the correct part.

Also consider an aftermarket inlet filter, that plate is pretty nasty dirty. Solberg is one brand to consider if the head is threaded for an NPT pipe and replacement filters are available.

 

[Mhardee86]

I was able to get new gasket and value from the link. The air compressor is now able to build pressure without issue. Thanks to all for the help!
I also noticed that there's a build up of moisture when using any compressor head. I've let the water drain from the drain plug, but I'll get a water separator for this issue.

Thanks again to all who helped out on this.