I tried to start the vehicle again - it ran for a couple of seconds - the tachometer moved. So I guess the cps is good?

I left the pressure gauge on the fuel line for 2 hours. It fell from 52 psi to 43 in the first 1/2 hour. Down to 36 psi in the next 1/2 hour. Then down to 30 psi in the next hour. Do I have a fuel pump or fuel regulator problem?