Central Pneumatic air compressors, like any air compressor, may start up and appear to be working as normal, only for them to then undergo difficulties in reaching their cut-off pressure. This article will provide you with the most common reasons why your Central Pneumatic air compressor won’t reach cut-off pressure, along with existing reader questions & responses.
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Reasons Central Pneumatic Air Compressor Not Reaching Cut Off Pressure
The most common reasons why your Central Pneumatic air compressor is not reaching cut-off pressure is due to failing or compromised components such as the gasket, intake valve, piston seal, or pump pressure valve.
It’s likely that your compressor will appear to be working fine, but during its cycling, the pressurized air is unable to flow into the tank due to a failed gasket. Another possibility is a failing air intake valve, where the air will blow right back out of the intake valve instead of being properly drawn into the compressor.
If the piston rings or their seals are flawed, the pumps will lose pressure and efficiency, resulting in reduced pressurized air being built in the compressor. The pump pressure valve may be faulty, therefore allowing the air that flows into the tank to be drawn right back out.
Other likely reasons a Central Pneumatic air compressor is struggling to reach cut-off pressure include system leaks. For more detailed information on these reasons visit our Air Compressor Won’t Reach Cut-Out Pressure Troubleshooting guide!
Reader Questions & Responses
Central Pneumatic Air Compressor – Central Pneumatic Air Compressor Troubleshooting
Question
I have a Central pneumatic Compressor that will start up fine but will shut off before pressure is reached. Central Pneumatic Air Compressor Won’t Build Pressure.
I have checked the Pressure Switch and it is fine. I.e. if the tank is holding 60 psi and I start it with a pressure switch set a 70 psi it will run to 70 turn off and if I bleed air off it will restart by itself as expected.
If I start from 0 psi it will shut off before it gets to shut off pressure. If I wait a bit reset button clicks and I can reset it and it starts again. Can It be a running capacitor/ starting capacitor or is it more likely just getting too hot from the motor getting to the end of its days? Any easy way to check?? These are cheap compressors so obviously don’t want to “waste too much”.
Response
You’ve checked the pressure switch Michael, and you say it’s fine.
When the compressor shuts off prematurely, is it the pressure switch that is shutting it off, or is the motor going off on reset?
If the pressure switch is toggling off power to the motor before its set point, then my money is on a bum switch.
If the motor is going off on thermal overload, then your guess about the run capacitor may be right on the money.
Can you check and let us know?
Central Pneumatic Air Compressor Won’t Reach Cut-Off Pressure – Central Pneumatic Compressor Troubleshooting
Question
I have a 3hp 21gallon central pneumatic compressor not reaching cut-off pressure.
I bought it at an auction and noticed that half of the air filter assembly was missing. I plugged it in to try and it pumps up to 50 psi good but no further.
I have taken the head off and the reed valve looked good piston looked good as well.
I did notice when it’s running it vents a lot of air out the oil filler cap. I have not disassembled the flap inside of the head. what do you think is wrong?
P.S. I have also messed with a pressure switch that’s not it either
Thanks, Steve
Response
Steve, good that you checked the valves.
A key clue for me though is the air bleeding out the oil fill cap. Where do you think that air is coming from?
Typically, that is a sign of worn compressor cylinder seals. The more wear, the more air that bypasses them into the sump instead of going into the compressor tank, and the more air that bleeds out the oil fill cap.
The seals in your compressor may hold until the tank pressure gets near the 50 PSI level, and then, the increasing back pressure forces the piston seal(s) to leak. Air will always follow the path of least resistance, so, it seems that it is easier to blow the cylinder seals open than it is to exit through the pressure valve and into the tank past the tank check valve.
Pressure at 50 PSI (or any pressure level) with the compressor running is also an indication of a gasket leak inside the pump. My rule of thumb is if you are going to tear down the pump to check things out, have a gasket kit on hand to replace them, and ensure that they are not the problem.
If you have any questions regarding a Central Pneumatic air compressor not reaching cut-off pressure, please leave a comment below, with a photo if applicable, so that someone can help you!
