Reciprocating-Type Air Compressor Won’t Build Pressure? Common Causes & How to Fix Them

When your piston air compressor runs, but won’t build pressure, your entire operation can grind to a halt, resulting in downtime, lost productivity and reduced efficiency that negatively impact the bottom line. This blog will help you identify common causes and potential solutions. Whether it’s a simple adjustment or a more complex mechanical failure that requires expert service, JHFOSTER is here to help you get back up and running as soon as possible.

First Steps: Simple Checks You Can Do Right Now

Often, the reason a piston compressor runs, but doesn’t build pressure is a minor issue with an easy fix. Your first step is to perform these simple troubleshooting tasks.

Check the Pump and Controls

There may be an unloader valve that doesn’t function properly, which can result in low pressure. A defective unloader valve can be identified by the absence of the “blow down” sound that should occur when compressed air is released from the valve or a constant leaking sound. 

Oil level, some compressors utilize hydraulic unloaders which prevent the compressor from creating air pressure when the oil level is low.

Inlet filter, a clogged inlet filter will greatly reduce compressor performance. 

Valves that may be leaking and in need of service. This may be identified by air leaking out of the inlet filter when the compressor is off or abnormally high head temperatures.    

Inspect Drain Valves

One common reason for pressure loss is a partially open or faulty tank drain valve. Check the drains to ensure that all drain cocks are fully closed.

Review Your Air Tools

It may be possible that a tool’s air demand (CFM) exceeds the compressor’s capacity. Or, a connected hose or tool may be leaking, which can result in a loss of pressure.

Summary of Common Mechanical Issues in Piston Compressors that Prevent Pressure Build Up

If the issue is not resolved with a simple solution, it may require additional investigation, such as:

• System Air Leaks: Leaks in hoses, pipes, fittings and couplings are the number one cause of pressure loss and wasted energy. There are three ways to detect leaks: Listen for hissing emanating from air compressor lines, which is a sure sign of a leak; apply soapy water to connections, joints or areas of pipe where the leak is suspected as soap bubbles will form and pinpoint the source of the leak. Once identified, leaks should be repaired as soon as possible.
• Clogged Intake Filter: Intake filters can become clogged with particulates such as dust, dirt and moisture found in the ambient air. When clogged filters are not changed, it can choke the compressor, preventing it from drawing in an adequate supply of air for compression. This is a critical maintenance issue that should be addressed immediately as it can cause compressor failure.
• Worn Gaskets or Seals: Gaskets, particularly the head gasket, are critical for sealing the compression chamber, which is necessary for proper performance and efficiency. A gasket or seal failure will prevent the compressor from reaching proper pressure levels.
• Faulty Unloader Valve or Check Valve: The unloader valve relieves pressure during startup, while the check valve prevents stored air from flowing back into the pump. A failure of either valve may result in pressure issues.
• Worn Pump Components: Internal wear on the pump itself, such as worn piston rings or valves, will result in a compressor that fails to build pressure when running. Worn pump components require the assistance of a professional repair service.

Frequently Asked Questions

Q: Why is my air compressor taking so long to build pressure?

A: This is typically due to air leaks, a clogged intake filter or internal pump wear. The system must work harder and longer to compensate, resulting in wear and tear on components, decreased performance, reduced energy efficiency and rising electric bills.

Q: How long should it take for an air compressor to build pressure?

A: This varies depending on the tank size and the CFM rating of the compressor. The key isn’t the exact time, but rather any noticeable change in the time it normally takes for the compressor to build pressure. If it suddenly takes longer than it used to, this is an indication that there is likely a leak or mechanical issue, such as a worn component.

Q: Why won’t my air compressor reach its full shut-off pressure?

A: This issue is often caused by a significant leak, a faulty pressure switch or a worn-out pump that can no longer generate the required pressure.

Q: How can I tell if my compressor pump has failed?

A: If it’s knocking or locked up.  In these cases, it’s usually more cost effective to replace versus performing a repair.

When to Call the Experts: Your Partner in Compressed Air Solutions

When an air compressor is running, but won’t build pressure, it can impact your entire operation, so the goal is to get your compressor back in working order as soon as possible. While simple fixes are possible, industrial air compressors are complex systems and can be difficult (and hazardous) to repair without proper training. However, when you partner with the experts at JHFOSTER, you can be sure to reduce downtime and improve system longevity.

JHFOSTER’s core air compressor service offerings include:

• 24/7 Emergency Service & Repair: We know you can’t afford delays. Our technicians are available 24/7 to get you back up and running as soon as possible.
• Comprehensive System Evaluations: A pressure problem might be a symptom of a larger inefficiency. Our in-depth evaluations can uncover hidden energy losses and save you thousands in operating costs.
• Preventive Maintenance Plans: Avoid future downtime with a tailored maintenance program designed to meet the specific needs of your operation.

Learn more about JHFOSTER’s air compressor services. Contact us today to schedule a service or request an evaluation.