I have a new system that consists of the followig:

1 1/4" brass foot valve to 1 1/4" poly pipe with 8' head and 325' horizontal run to a 1/2 hp shallow well jet pump into a bladder tank.

My problem is that I can't build greater than 32 or so psi, the pump will just run and run. The needle on the pressure gauge bounces a little

I have done the following:

checked foot valve, all is good
bleed all air from intake line
pump never loses prime or built up pressure when off
took apart pump and made sure in flow and impeller were clean
checked air pressure in bladder, it's at 28lbs for 30/50
isolated the system by closing main valve right after the system

I have lowered the on off to 32/15 just so we can have water and the pump won't run continuously.

Could it be because of the long run of the supply line.

Any help would be great.