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Air Compressor Won’t Reach Cut-Out Pressure Troubleshooting

Published Categorized as Air Compressor Not Reaching Cut Off Pressure, Air Compressor Troubleshooting No Comments on Air Compressor Won’t Reach Cut-Out Pressure Troubleshooting

When your compressed air system fails to reach sufficient pressure for any given application – whether that be auto body painting and detailing or powering your various pneumatic tools – your application suffers. A serious lack of adequate pressure can cause an air compressor to not reach its normal cut-out pressure, and instead run for extended periods of time.

This article will provide you with all the relevant information on why your air compressor won’t reach cut-out pressure, and some troubleshooting tips to fix the problem!

Table of Contents

Why Does My Air Compressor Not Reach Cut-Out Pressure?

The most common reasons why your air compressor is not able to reach cut-out pressure is likely due to failing or compromised components such as the intake valve, gasket, piston rings and seal, pressure switch, or pump pressure valve.

Although it may seem like your compressor is initially working fine, during its cycling, the compressor is unable to build pressure above a certain point due to a number of possibilities. If your gasket is failing, the pressurized air won’t flow into the tank. Or, it could be your air intake valve that is allowing the air to blow right back out of the valve instead of being drawn into the compressor for compression.

If the piston rings or their seals are defective, the pumps will lose pressure and compression strength, which ultimately reduces the pump’s efficiency to produce compressed air. The pump pressure valve may be faulty, therefore allowing the air to lose pressure and not properly flow through the airlines into the tank.

When pump valves fail to build up pressure in tanks, they may not be able to stop the air compressor from running continuously. Hence, why your air compressor is running but not reaching cut-out pressure.

Air Compressor Won't Reach Cut-Out Pressure Troubleshooting

Air Compressor Won’t Reach Cut-Out Pressure: Troubleshooting Steps

So, if your air compressor won’t reach cut-out pressure, you should be able to diagnose and fix the problem by following these troubleshooting steps:

  1. Conduct a pump-up test
  2. Inspect system for leaks
  3. Clean filters
  4. Inspect system valves
  5. Evaluate belt condition
  6. Inspect pump rings
  7. Inspect air/oil separator

Let’s take a look at each step, with more detail provided on how these failing components can stop your air compressor from reaching cut-out pressure.

1. Conduct a Pump-Up Test

The first step, to be absolutely sure, is to conduct a pump-up test. These can provide a great insight into the amount of time your compressed air system takes to build pressure. To conduct the test you will need to completely empty the air tank.

Once emptied, you can close the discharge valve, and then record the amount of time it takes for your compressor to achieve your desired PSI from 0. Of course, the maximum pressure of an air compressor will vary by model, so if you aren’t sure of your exact cut-off pressure or the time frame in which a certain pressure level should be reached, consult your user’s manual or contact your manufacturer.

Note: If you’re absolutely certain your air compressor isn’t reaching cut-out pressure, you can skip this step and go straight into step 2. However, it can be useful to measure the amount of time it takes to reach a low pressure of say 30-50 PSI (if it can), and compare it with the time in which it should be reached.

2. Inspect System for Leaks

Probably most air compressor users’ initial thought, and one of the simplest checks is system leaks. First, you must adjust your air demand settings to the appropriate level and then check for any potential leaks. Leaks are a very common culprit of any air compressor building pressure but not being able to reach cut-off pressure.

You should survey your air tank and fix or replace the tank if you discover leaks. Ensure all air tube fittings are tightened appropriately and inspect all other components. We have some useful pages on air compressor system leaks available that will help you:

3. Clean Filters

For this step, it is advised to clean all your filters present in the air compressor system. First, check your air inlet filter by loosening the wingnut, removing the housing cover, and inspecting the filter. You must ensure it is clean and clear of any debris and other particulates buildup.

Conduct periodic preventative maintenance to ensure all of the filters on your air compressor are clean. If necessary or recommended, replace filter elements or the whole filter based on your environment.

4. Inspect System Valves

The next step in troubleshooting a compressed air system that won’t reach cut-off pressure should be examining all your machine’s valves. First of all, make sure the inlet valve is capable of opening completely and the drain valve at the bottom of the air tank is sealed suitably tight.

After checking the inlet and drain valves, make sure the unloader valve is not leaking or experiencing any sort of problems. This is a very important step. The unloader valve, or safety valve, is designed to open to relieve excess air pressure in the case that the pressure switch fails to turn off the compressor at the cut-out pressure setting. An issue with the unloader valve can heavily impact a machine’s ability to reach its cut-out pressure.

In the case of reciprocating compressors, their most common reason for an inability to reach cut-out pressure is a defective reed valve. A faulty reed valve can exhaust air out from the air inlet on single-stage reciprocating air compressors or, through the intercooler safety valve in the case of a two-stage compressor instead of passing it through the intercooler, through the second stage piston, and out through the discharge.

A great indicator of a problem with the reed valve is your air compressor plateauing around 30-70 PSI. The reed valve can be found on the top of each cylinder. To replace the valve, you will need to first loosen the cap screws, remove, disassemble, replace the reed valves and gaskets and reattach the head plates to the cylinder. For more information on these, visit our Air Compressor Reed Valve Troubleshooting guide!

Note: It may also be worth opening your drain valve and looking for any oily residue. Every oil-lubricated compressed air system will experience a natural level of oil carryover, however, this should be minimal. High levels of oil carryover will prevent a compressor’s ability to reach cut-out pressure.

5. Evaluate Belt Condition

If your compressor operates on a belt drive, it could be a belt malfunction that is the culprit of your air compressor not reaching cut-out pressure. To check the belt, first, make sure your machine is turned off and the power disconnected from the wall socket. Then you can remove the rear section of the belt guard. Loosen the motor mounting bolts in order to tighten or, if necessary, replace the belt.

To replace the belt, slide the motor in the direction of the pump, gently remove the belt from its pulleys and install a new belt(s), before returning the motor to its proper position. Tighten the motor mounting bolts and adjust the belt tension as required. Finally, reinstall the belt guard and you’re good to go! Visit our Air Compressor Belts Guide for more information.

6. Inspect Pump Rings

Defective pump rings will no longer be able to seal the air in the cylinders, preventing excess oil from passing downstream, and being critical in ensuring an air compressor’s ability to reach cut-off pressure – as they should.

When pump rings become worn, the air compressor pump will be unable to effectively compress air which can greatly reduce the volume of air the pump is able to produce. If this is the case, you will likely need to rebuild or replace the pump.

If both the pump and the pump rings seem to be operating correctly, check the valve plates to ensure they are sealing properly – if you haven’t already. Visit our Air Compressor Pumps Guide for more information.

7. Inspect Air/Oil Separator

On rotary-type compressors that are oil-injected, after checking the oil levels, you should assess the differential pressure across the air/oil separator. If the air/oil separator is fouled in any way, whether that be clogged or damaged, it could be preventing the successful separation of oil and air within the compressor.

Therefore, this could hinder the machine’s ability to reach the cut-out pressure level and thus increase operating costs. When it’s necessary, replace the air/oil separator.

FAQs (Frequently Asked Questions)

Why is my air compressor not cutting out?

Your air compressor is not reaching cut-out pressure likely because you have a defective component such as the head gasket, intake valve, pressure switch, or pump pressure valve, to name a few. It’s also possible that you have an air leak somewhere in the system which is blocking the air compressor from building pressure past a certain point.

If you have any questions regarding an air compressor not reaching cut-out pressure, please leave a comment below, with a photo if applicable, so that someone can help you!

By Aidan Weeks

A passionate Mechanical Engineer with endless enthusiasm for fluid power - building off the back of over 18 years of high quality contribution and discussion stimulated by Bill Wade here at About Air Compressors. With both practical and theoretical experience in pneumatics and hydraulics, I'm putting my knowledge to work - and working my grey-matter through my research, assistance and publishing work here at About Air Compressors. Feel free to reach out any time! P.S. A HUGE shout out to Doug who really offers such great value to all visitors to About Air Compressors - once again, feeling like I'm standing on the shoulders of GIANTS by getting to work alongside such a great community

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