Compressor Pressure

Compressor pressure problem?

With so many questions and responses about why an air compressor does not build pressure and compressor pressure problems, I am adding a number of pages of information to address this issue. This is another in this series of information pages.

Montgomery Ward compressor won't pressurize
       - tank "check valve" issue?

By: James, San Jose, CA. My compressor is a Montgomery Wards brand 220v/1.5 hp 20 gallon model, with a Franklin Electric motor, a two-cylinder compressor, and a Kargard Industries tank. The date code on both the tank and the motor are 1972.
montgomery ward air compressor

It seems my compressor has the same symptoms as a previous poster - it will not pressurize the tank above ~40 PSI. When the compressor is first turned on with the tank unpressurized, I can feel the cylinders sucking in air as they should; but as the pressure builds, more and more air is pushed right back out the intake valve. As with the previous poster, I disassembled the heads on my compressor to check the valves. They're just flat reed valves, and appeared to be in fine condition, just a little dirty. I cleaned the valves, head, and ports copiously, replaced the gaskets with new ones, and reassembled. But this did not solve the problem. Neither does changing or even removing the air filter.

Bill, you mentioned something about a "check valve going into the tank" in regards to the previous poster's problem. While his problem turned out to be a head gasket issue, it doesn't appear that mine is, so I would like to know more about this check valve. What is its purpose, where exactly is it located, and how do I test it? Thanks for the help! -James

My response: Hello James. Thanks for visiting, writing in, and including a photo. It sometimes makes answering so much easier. If you look at your photo, see where the air line from the piston head turns and runs down to the tank on the left? Usually, the device that connects that air line to the tank opening is a check valve. It's purpose is to keep the air in the tank as the piston compresses it. The higher pressure air flows down the line, through the check valve, and into the tank.

If this check valve isn't seating properly, or has failed completely, then air can't stay in the tank. This may be an issue for your compressor. Best to make sure the tank is empty, the compressor is unplugged, and then disassemble the fittings at the tank, and examine the check valve. It should seal the air in one direction. Reassemble after cleaning (if needed) and see if this makes any difference, OK?


Jan 09, 2012 Looks like a Champion pump by: Smithereens

Sorry to barge in here, but I saw a lot of posters asking about the pump on the Ward's unit. That looks to me like a Champion pump, and parts are still available for those. They were used on a variety of brands (Speed Aire, for instance), and they made a million of them, much like the cast iron Campbell Hausfelds. Check with Grainger or Champion - I think you will find the parts. - Mark

Compressor will not build pressure?

By: Mark, McComb, OH. I think the reed valve is not sealing, but it looks okay. Everything in the head looks clean and in good shape. The piston has good suction. What can I do to repair it if it all looks good?

My response: Howdy Mark. When the compressor is running, is there a puffing or a pulse of air out the intake valve? You might pull the intake filter and carefully place your finger near the intake port to feel if there is pressure. If no air is coming out, then logically the only place the compressed air can go is into the tank.

Now, assuming that there is no mechanical issue with your compressor, then why isn't the pressure rising? Well, if you have a gasket failure inside the compressor head, then the air is simply moving back and forth inside, and not getting pushed into the tank at all. I suspect that may be the reason why your air compressor will not build pressure.

Comments from Mark. Found the problem - by: Mark. When I posted my original question, I thought that everything in the head looked good but I did not realize that there was another gasket and spacer still stuck to the head when I removed it. I removed the spacer and gasket and found that the gasket was blown out between the intake and exhaust ports. I made a gasket from cheap gasket material and it has been working good for over a month.

Compressor will not build pressure?

By: herbert smith, roebuck, sc 29376. Compressor blows air out the filter on top of compressor and will not build pressure above 50 psi.

My response: Howdy Herbert. If it is the intake port that is blowing air out when the compressor is running it would suggest to me that your intake valve has failed, and your compressor is pulling air in, and then some of it is blowing back out the intake port, and not compressed into the tank. At 50 PSI, the intake and out-blow seems to be almost equal, and the pressure won't get any higher than that despite how long the compressor runs.

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