I purchased a new booster pump which comes with the cilinder and auto pressure valve.

The pump should start at 20 PSI (when you open a tap) and cut off at 40 PSI (when you close the tap). However, I can not get the pump to cut off when reaching 40 PSI.

Are there any expert out there who can give me ideas. It runs continuously.

To lower the factory set cut off pressure, you can adjust a nut on the spring of the pressure valve, but when I adjust this, the pump goes on and off, on and off continuously.

I have also increased the air pressure in the cilinder, and tried by lowering it, but nothing works.

I also do not have any leaks on the inlet or outlet.