by Alan Young
(University of Mich-Ann Arbor)
We have a 150 liter Jun Air Model 4000M-150B Compressor.
I recently drained the entire system and replaced the intake filters and a check valve. I turned it on to re-pressurize the system. I am only charging the tank at this point-not the lines.
The cycle should shut off at @125 psi. It has taken 45 minutes to get to 75 psi at which point I shut off the compressor.
This seems to be an excessive length of time for re-pressurizing the tank.
I have checked for leaks and can’t find any-Seems that there is difficulty with air getting into the tank. The tank holds pressure over night as I shut it off and it remained at 75 psi.
Hello there Alan. It would be interesting to know how come you felt the need to change the intake filters and the check valve? Were you seeing an increasing fill time before you made the change?
As long as the check valve is installed correctly – with air passing the right way and air not passing the incorrect way – replacing the check valve and intake filters should not have affected the fill time.
Coincidences happen, and I suppose it is possible that your has Jun Air developed a valve problem, or gasket leak, at the same time as you made the changes you did.
See the troubleshooting section for links to pages about why air compressors do not build air pressure properly for some things to check and then please post a comment here with findings.
Thanks for the photos. They always help.
Jun-Air Compressor Cycle
I should have probably given more info to start. The compressor was taking along time to fill and I followed the JA manual in order-replace intake filters-Did that still no change in the long pressurize time- checked for leaks every where with soap solution-no leaks found, Next step is to replace the check valve so I did that-still taking along time to reach pressure-This is the tank only-I have shut off the valve leading from the tank to the rest of the system. The manual no is saying to replace piston rings- I am no in the process of taking apart one cylinder(Two pumps each with two cylinders)to check the rings—
Thanks for the update.
Yup, could be piston rings, could also be the valves, and if you are working inside the pump, replace any gaskets you find too.
Jun-Air Compressor Exploratory Surgery
Thanks for the response to my post regarding our compressor. After opening up the unit I am looking at the possibility of replacing gaskets and rings. This link has a series of pictures showing what I have found so far….
Excellent Alan. Thank you for taking the time to share this link with us.