In most cases, an air compressor at an industrial facility or business needs to operate around 120 PSI. Of course, the exact PSI (Pounds Per Square Inch) you need will depend on your application. For every 2 PSI above 120, around 1% of more power is needed.

Needless to say, that an air compressor that won’t build pressure is preventing you from working efficiently.

If your air compressor won’t build pressure, it could be a failing pump motor, a clogged air inlet filter, or something as simple as poorly adjusted air demand. Other common reasons for an air compressor to be unable to build and maintain pressure are worn out valves, belts, and pump rings.

Start and run capacitors are a common culprit when a single phase air compressor won’t hold pressure. It could also be a failed oil separator, power supply, or pressure regulator.

My Air Compressor Won’t Build Pressure – Why?

If your air compressor cannot build an adequate amount of pressure, it will cause your air compressor to for much longer periods of time without ever reaching its cut-out pressure. This causes an advanced amount of wear and tear on your machine. 

If you have a single-phase motor, then such a scenario will cause your start capacitor to overheat and prematurely fail. This is not the only thing you have to worry about. Also, if you run your air compressor on too low of a pressure it can cause excessive oil carryover which will result in major losses.

It’s important to know how to properly size your air compressor to maintain desired pressure levels and how to troubleshoot it in the event your machine’s pressure falls below your desired pressure.

1.Check Your Pump 

Performing a pump test will indicate the amount of time it takes for your compressed air system to build pressure. To do this test, all you have to do is empty the air tank, close the service valve at discharge, and take note of the time it takes for the compressor to go from 0 to the desired PSI.

It is important to keep in mind that the maximum pressure of a given machine will vary. So, if you don’t already know your cut-off setting or the time it usually takes to reach a given pressure, check with your manufacturer to get those specs.

2.Clean Your Filters

It’s always good to check your air inlet filter. Just loosen its thumb screw or wingnut, take off the cover, and take a look. An air filter will, ideally, be free of dusty, dirt, and debris.

Conduct periodic maintenance to ensure all of the filters on your air compressor are clean. Replace filters as often as recommended or necessary based on your environment.

3.Perfect Your Air Demand And Check For Leaks

You should always make sure your air demand is set to what you need. It’s important to match these aspects to maintain the highest efficiency. Leaks are an extremely common reason why an air compressor won’t maintain pressure. 

A study was done by a company called ‘Efficient Plant’ that showed that facilities that don’t have any leak management protocols end up losing about 40% of their total compressed air production to leaks.

So, make sure to thoroughly inspect your air tank for leaks. Also, make sure that your air tube fittings are properly secured.

4.Inspect All Valves 

If your air compressor won’t build pressure, the next thing to check is your air compressor’s valves. Ensure that the inlet valve is able to properly open and make sure the drain valve is totally sealed.

Another super important thing to check for is oil passthrough. You can examine this by opening your drain valve and seeing if there is any sort of oily residue. 

Remember, every oil or lubricant-based air compressor is going to have some level of oil carryover, there should be a very low amount of oil that actually ends up in the air tank. So, if you have high levels of oil carryover, it can make it really hard, if not impossible, for your compressor to build pressure.

You should also ensure that the safety valve does not have any kind of leaks. Remember, the safety valve is designed to open and relieve excess air pressure.

So, if your safety valve is not working right, your air compressor will not be able to build pressure even if there is nothing else wrong with your machine.

If you are one of the few people that are still using a reciprocating compressor, then the first thing you want to check is your reed valve. If it’s defective, it will exhaust from the inlet if you have a single stage unit. 

If you have a 2 stage reciprocating air compressor, it will shoot air out of the intercooler safety valve if your reed is bad. So, if your machine is inexplicably topping out at 60 or so PSI, then you may have a problem with your reed valve. 

The reed valve is located on the top of each cylinder. All you have to do to replace the valve is loosen the cap screws, remove the reed assembly, disassemble it, replace the reed and gaskets, and put it back together.

5.Check The Belts

If your air compressor uses a belt to operate, a worn out belt may just be the reason your air compressor won’t build pressure. Belts are super easy to check and replace.

Just make sure the compressor is turned off, then remove the rear section of the belt guard. After that, you will need to loosen your compressor’s motor mounting bolts in order to tighten or replace the belt. 

Inspect your belt for any dry rotting, tears, or other damage. If you need to replace it, simply slide the motor towards the pump, carefully remove the belt from its pulleys, and install the new belt.

After that, all you need to do is tighten the motor mounting bolts and adjust the belt tension. Also, make sure to put the belt guard back on.no

6.Check Pump Rings  

Pump rings are used to seal the air inside the compression cylinders. These also prevent excess oil from passing downstream into the tank. These sealing rings are necessary for the air compressor to build pressure.

So, if your pump rings are worn out, the pump is not going to be able to compress air effectively. This will lead to a reduction in air volume and it will put your air compressor in a position in which it won’t be able to build pressure.

7.Check The Capacitors

If the capacitors in your compressed air system are going bad, the motor won’t be getting the right amount of power. 3 phase air compressors don’t need a starting capacitor, but single-phase systems do because there is not enough current to start them. 

There are several different failure-modes for capacitors and one of them will make it so your motor will run, but not at its normal operating speed. This will definitely cause your air compressor to not be able to build or maintain pressure.

If you are uncomfortable with servicing the electrical aspects of your air compressor, then you may want to call an electrician so they can properly inspect and repair your machine.

8.Take A Look At Your Oil Separator

If you have an oil-cooled rotary-type air compressor, make sure to measure the differential pressure across your machine’s air/oil separator. If the separator is damaged, dirty, or clogged, your compressor will be unable to separate the air from the oil.

This will prevent your machine from being able to reach its cut-out pressure and will absolutely increase operational costs.

9.Check Your Power Supply

There is a chance that the wiring in your home, office, or shop has some sort of problem. If you are running an air compressor on a heavily loaded circuit, it can prevent the machine from getting the amount of power it needs to operate correctly.

So, make sure to test and service any breakers, fuses, or any other power equipment in between your compressor and your breaker box.

10.Check Your Pressure Regulator

If your output pressure regulator is starting to go bad, it can seem like your air compressor won’t build pressure when it really is.

Remember, the main output pressure regulator is responsible for delivering the compressed air to whatever equipment you happen to be powering. So, if that regulator is not able to do its job, it will be unable to send all (or in some cases any) compressed air out of your machine.

Conclusion

When your air compressor will not build or hold its pressure, it will cost you money and time. It could possibly cost you a lot more than that if you depend on an air compressor for the day to day operations of your business. 

If your air compressor is struggling to build pressure or if your air compressor won’t build pressure at all, there are many possible causes. The first thing to check is your air filter.

If it’s not clogged, your pump motor may be on the way out or you could have worn out belts, valves, or pump rings.

If you have a single phase compressor, you may want to check your start and run capacitors and regardless of the type of compressor you have, it could be your oil separator, power supply, or pressure regulator going bad.

We hope this article helped you figure out why your air compressor won’t build pressure. Thanks for reading!