Compressor; why not build pressure; simple diagnosis and remedies to get your wo

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Why Won't Your Compressor Build Pressure?

Compressor; why not build pressure?

It seems of late that of all the questions about troubleshooting compressors I get (and I get so many now that I have a real hard time trying to catch up) it's the "why won't my compressor build pressure?" that's become the most prevalent.

So, why won't your air compressor build pressure?

Please note that if your compressor won't start then you will want to visit this page about compressors that will not start.

This page addresses the issue of compressors that start OK, but reach a pressure-plateau that's below the normal cut out pressure level, and then stays at that too low pressure without gaining greater pressure in the tank while continuing to run.

Here's what you need to look for when your compressor will not build pressure.

My #&^#* Compressor Will Not Build Pressure. Why?

Power Supply

It's a bit of a stretch, but if you are starving your air compressor of enough electricity, it is possible that the motor can generate a certain level of pressure in your tank, and then not exceed that pressure as there just isn't enough electricity reaching the motor to allow it to work hard enough.

First thing then is to make sure that your compressor is getting the full 15 amps from your breaker (use a heavy extension cord if you must use one) by plugging the power cord that came with the compressor right into the socket.

Also, make sure that nothing else that might be powered by that same socket is trying to run at the same time your compressor is. Compressors will run best with full electrical supply from a circuit, over the shortest electrical cord possible!

Did this solve the problem? In not, please read on.

Does Your Compressor Leak?

Let your compressor come up to whatever pressure it will. If the pressure reaches a certain level and then won't go past that pressure level, then either turn it off or unplug it.

Listen!

What you are listening for is an air leak. Since most compressors are quite noisy, you won't be able to hear a leak with the compressor running.

Get your ear down close to the compressor. In particular, check to see if you have accidentally left the tank drain open somewhat.

Another spot to check carefully is the unloader valve. The unloader valve may have "burped" a bit of air when you turned off the compressor, but it should not have air bleeding out of it all of the time. If that is happening, this may be the reason that your air compressor cannot compress air past a certain level.

If the unloader valve is leaking, you need to get it fixed.

Did this solve the problem? No? Then please read on.

The Valve Thing

Compressors have valves that allow air to enter the cylinder area when the piston is moving down, and allow the air to be directed into the tank line when the compressor piston is on the compression stroke.

Low cost compressors have low cost reed type valves.

If either of these valves fails (breaks or fails to seat properly) then your compressor will run all day and never build pressure.

If it is the intake valve that has failed, then the compressor will draw air in when the piston descends, but then that air will blow right back out of the intake valve when the piston is in the compression stroke. Air always takes the route of least resistance, so some of that air may be entering the tank, which is why the compressor reaches a threshold pressure, beyond which it won't go.

If it's the exhaust or to-the-tank valve, air will flow into the tank on the compression stroke, but then be drawn right back out of the tank as the piston descends to try and draw more air in through the intake valve.

A quick check is to remove the intake filter and feel if air is moving in and out of that opening. If so, your intake valve may have failed.

For most of us, a failed reed valve(s) mean a trip to the compressor repair shop.

Before deciding to do that, read on.

The Gasket Issue

I'm going to guess that it's a method of reducing metal and saving money. On low cost compressors, the flow path of the intake air is often separated from the flow path of the air to the tank by a thin gasket.

Gaskets shouldn't fail if they are not misaligned through removal or replacement, or if they have sufficient mass to withstand the pressures exerted on them by the compressing of air. But, good gaskets cost more money than cheap ones, and cheap ones sometimes fail.

It is possible that your compressor is working fine, but as it is cycling, the air is flowing back across that failed gasket as the piston finishes its compression stroke.

Once again, if your compressor intake is "huffing and puffing", that may be the reason. You need to tear the compressor down to check.

The Economics Issue

And now we have to consider the economics. To change out the reed valves on a small DIY type air compressor will take about one hour of shop time, according to the repair depot I spoke to. What do they charge; $40 / hour, maybe more?

Then there is the parts themselves. Many of the DIY type air compressors come from another country, and sourcing parts for these units is time consuming, if parts are available at all.

So, do you spend the $75 or more dollars to fix your $150 compressor or not? it's your choice!

Folks, if these hints do not provide the answer for you, just fill in the form on this page and maybe we (me and the thousands of readers who visit this site each month) can help further..