There's a control,usually under the housing that adjusts the pressure it trips off,and back on again.Sounds like your's is set to low.even if the piston and bore are worn,it'll still go above 90psi,it'll just take longer.Have your's checked or try yourself,its fairly intuative.All 3 of mine have the pressure switch under the on/off button,just remove the black cover,should be wired to mains,with a connection into the tank for the pressure.
caine, December 2008