Why is it a compressor will not build pressure? The motor runs, the pump sounds like it’s running, but the air pressure in the tank either doesn’t rise at all, or rises to a pressure point and then the pressure stops rising, even though the compressor continues to run and run.
A compressor is a pump. That pump pulls in free air from the atmosphere and is supposed to drive it into the tank, and that increases pressure in the compressor tank.
Different styles of air compressors, reciprocating versus rotary screw form example, accomplish this with different methods, yet they pretty much all do the same thing, suck in air from around the room or through an outside air intake and drive that air into a tank.
What to check on an air compressor when the compressor will not build pressure?
The air compressor reed or flapper valves (also known as the intake and pressure valves, or suction & discharge valves) are a common cause of why an air compressor will not build pressure.
The image below shows the pump of a small air compressor, and the valves on this model.
If the compressor valves or gaskets are what the pump problem is, then it will be necessary to disassemble the pump to repair that problem.
Before you do that, there are other reasons why an air compressor will not build pressure. Pretty much all of them are found here.
Get some help with a compressor that will not build pressure!
You can certainly use the form to ask a question about what to do when your compressor will not build pressure.
Please provide as much information about what your compressor as possible. The make, the model, the age of the compressor, how much it is used, the type of power supply… anything that you can think of that will help us (myself and the many visitors) help you with this air compressor problem.
If you’ve got a suggestion about solving the compressor problem that someone else has posted on this page, please add a comment if you would.
My thanks…
Bill
my hitachi 8gal gass compressor. today a hose blew off this fitting for like 10 seconds before I got it back on and then now I only get 50lbs of pressure. do I start taking the motor appart? or do I just buy a new unloader valve cause is that whats breaks when something like that happens?
I have a Craftsman air compressor model # 919.155730 that doesn’t build tank pressure. I’ve rebuilt the pump w/ new cylinder, piston ring, all related o-rings & gaskets. Old cylinder was slightly scored. While I had it disassembled, I went ahead and replaced Reed valves as well. After reassembly, air still comes out of intake as before I rebuilt the pump. The motor runs flawlessly. Could the check valve in the tank be stuck closed forcing air back through the intake? I cleaned all surfaces on head well & nothing else has been replaced. Compressor has worked well since 1992… Read more »