Compressor running fine but unit never builds up enough to cut off

by Terry
(Travis Bridge, AL)

5.5  hp. 25  Gal compressor

5.5 hp. 25 Gal compressor

5.5  hp. 25  Gal compressor
5.5  hp. 25  Gal air compressor
5.5  hp. compressor
5.5 HP air compressor reverse view

5.5 hp. 25 Gal motor is running fine but unit never builds up enough to cut off.


I checked the tube going into the tank and it is pumping plenty of air into the tank.

The inside of the compressor seems fine, a little wear inside piston sleeve but no scratches. Metal flaps (?) seem fine and gasket in one piece. I have plenty of intake as it will suck my hand to it easily. I can detect no leaks.
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Hi Terry... without the model number or a photo it's pretty hard to see the details of your air compressor and to help you figure out why it runs and does not build pressure.

It would also help to know what pressure the tank gets to before advancing further. I suspect that the tank pressure is getting up there, maybe 60 PSI or more?

When you say "I checked the tube going into the tank and it is pumping plenty of air into the tank " and "I have plenty of intake as it will suck my hand to it easily ", these are good checks, but really not empirical. They "feel" right.

Here's what I think is happening. When the tank pressure gets to a certain point the backpressure load on the pump blows open the gasket that looks fine when it's not under pressure.

This were my air compressor I would be rebuilding the pump with a new gasket and valve kit. The valves are the "Metal flaps (?)" you refer to.

Cheers,

Bill

Comments for Compressor running fine but unit never builds up enough to cut off

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Jan 05, 2013
Running again
by: Terry

Bill, the compression ring did the job! My unit is building up pressure as normal and working fine. Thanks for all your help and patience, you saved me a lot of money buying a new one.
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Very glad to have been of assistance, Terry.
Bill

Dec 16, 2012
Oil fill vent
by: Terry

Bill, I am sorry, where is the oil fill tube vent? I am not following you.
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Terry, as I mentioned earlier, I could not find info on your model on line, nor did I find a photo.

I am assuming that your compressor is oil lubed? If so, it has an oil fill tube.

If yours is an oil-free model, meaning you do not have to add lubrication, then there will not be an oil fill tube.

If you wish, please start a new thread, and upload photos from all four sides of your compressor, and we'll have a look.

Cheers,

Bill
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Dec 17

Terry provided some photos which are now uploaded to this page.

Unfortunately, with reference to the oil fill vent bleeding air, none of the photos show one, and the one photo missing is of the back side of the pump, where there might be an oil fill tube.

As you can see, Terry writes that the compressor runs well, but the pressure in the tank takes a long time to get to 35 PSI.

He has replaced the valves and gaskets in the pump, and feels strong suction on the intake, and strong outflow on the port of the air tube down to the tank.

The only other thing I can think of was that the piston seals themselves are leaking enough that air simply bypasses them back and forth from the sump in to the pump compression chamber and then back into the sump, rather than into the tank.

Any other thoughts?

Dec 15, 2012
Air Output
by: Terry

Bill, I can not totally stop the air output with my finger. I can stop it pretty much but is ia a good force trying to keep my finger pushed away. Thanks .
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Terry, you should not be able to stop the outflow with a gloved finger. If you can, that still suggests that there is a pump / valve problem.

Tell me, while your compressor is running, and particularly if you can hold a finger over the outflow port, can you feel air blowing out the oil fill tube vent?

Bill

Dec 13, 2012
Intake Check
by: Terry

Bill, yes I seem to have plenty of air intake at the port.
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Make sure that the intake filter isn't plugged, Terry. If it's in good shape, than shut the compressor down, dump the air, and remove the line from the pump head to the tank.

Start the compressor, and wearing gloves, put a finger over the hole or port and try to stop the air output from the pump head while the compressor is running.

Can you even block the air a bit, or does the outflow push your finger off the port?

B.



Dec 11, 2012
Still Not Building Up Air
by: Terry

Bill,
Installed a new valve kit as well as a gasket kit today and no change. My unit still does not build up any pressure as previously noted. What should I look at next?
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My, that must be disappointing for you?

Pull the intake filter, and with the compressor running, are you feeling strong suction at the intake port?

B.


Nov 30, 2012
Follow up
by: Terry

Bill, the model number on my unit shows 91916523 but the Sears site gives me the choice of 919165230 or 919165231. Both these diagrams show the valve plate assembly as part Z-AC-0032 but then they do not list my model number as one this part fits. I am very confused. Any clues? Got the tank check valve off and it seems ok, no blockage and I assume it blows in only one direction.
Thanks (again) , Terry
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Yes, the check valve's purpose is to keep the air in the tank, so a check valve is also known as a one-way valve to fulfill that purpose.

In terms of parts for your compressor, if there is a different model number shown on their site, then it likely won't suit your compressor.

They have a phone number to call. Did you try that?

I expect that it's the valves or gaskets in the pump that are causing your compressor problem.

B.

Nov 29, 2012
Questions
by: Terry

Bill, a couple of clarification points if you could. First, you refer to the tank check valve, is that what I call a pop off valve near the gauges or is it in the tank where the tank fills with air? Either way, what do I check for? Also, what is included when you say get a gasket kit? The o ring within the valve assembly and what others? Sorry I am such a novice, you have been a giant help. Terry
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Terry, please see the check valve page for a description of what it is and what it does. You just want to make sure it works, nothing impeding air flow in the one direction and that the air is blocked in the other.

I tried to find parts info on your air compressor but that model number does not exist anywhere on the web that I could find. So, make sure it is the right model number, will you?

In order to advise what is in the gasket "kit", assuming there is such a thing for your model of Sears air compressor, I would have had to find it.

Essentially, any gaskets in the pump are what I would replace, particularly those between high and low pressure areas.

B.

Nov 29, 2012
Never builds up
by: Anonymous

Bill, thanks for your insight. The model number is 919165231 and it is a real struggle to get it to 35 lbs, takes about ten minutes. Does it still sound like a gasket and valve kit is the solution? Terry
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Terry, absolutely. But I did say to check the tank check valve first I believe? If not, do that.

From what you've written, it were my compressor, I'd be putting in a new valve kit, and to be sure, a gasket kit as well.

B.


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Problems compressing to 150 psi

by Spencer
(South Riding, Virginia, USA)

I have searched and read just about everything I could about this. I have a 1.1 hp single cylinder craftsman 17 gallon compressor (150psi max). It is a couple years old but used about 10 times to fill car tires and power an impact gun twice.

Problem is that is kicks on at about 100psi when being depleted and goes up rapidly until it hits about 145psi, then it takes about 10 minutes to get from 145 to just 150 (max). After a bunch of basic troubleshooting and leak detecting I decided that this was probably an issue that happens while the machine is operating, so I took a look into it internally.

I removed the head to check out what was going on and found that all the valves and gaskets were in brand new condition with no visible damage or any excessive wear. I did find, however, that when looking at the piston moving up and down while I manually cranked everything.....I could see light around the piston seal/rings.

Is it possible that there is room for heat expansion within the cylinder sleeve that would take up this slack or is it that I don't have everything bolted together, thus making the piston move up and down sloppily? Or is the piston seal/ring not mated to the sleeve perfectly....aka...China crap?

Thanks for any input on this....

Spencer

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Bill says...

Could be any of them, but I'd go with the last.

Is it a lubricated compressor? If so, you could see how much lube oil gets into the tank, and that would corroborate the piston seal issue.

Bill

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22 gallon oilless air compessor not building any pressure

motor runs fine blowing air out at muffler is muffler the problem
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No, I don't think the "muffler" (I think you might mean air intake filter?) is the problem.

Remove it and feel for air blowing out the intake port.

I suspect you will find that air is huffing out in time to the piston cycling, and that means, at the very least, your Sears air compressor has an intake valve failure.

See the troubleshooting section on the site map page for more things to check.

Cheers,

Bill

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Compressor trips breaker?

MY AIR COMPRESSOR ONLY RUNS ABOUT 5 SECONDS
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Friend, it would be good to have a bit more information about troubleshooting your air compressor than you have provided.

Please, as a comment here, provide the following:
Make, model, years in use, and what the power supply to the compressor is.

We'll all try to help if we can.

Cheers,

Bill

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Feb 24, 2015
Craftsman won't build pressure
by: Bill

Arnold, see the troubleshooting page about air compressors that run but don't build pressure for some things to check. If you still have questions, start a new thread please.

Bill

Feb 23, 2015
builds to 80 and continues to run
by: Arnold

My compressor builds to 80 and continues to run but does not build higher or shut off. Craftsman 919.167320 , 33 gal

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