No prime sound from pump pressure is just for a sec then drop to oIf you have pressure the pump is priming. You have a leak somewhere. Could be fuel pressure regulator, leaky injector, pump check valve, leak in the coupler between the pump and the hanger.
You may not be explaining the problem correctly. If the pressure goes to 45psi when the key is first turned on then the pump is priming. It only primes for a couple of seconds when the key is first turned on. If the pressure drops immediately then there is a leak somewhere. Does the pump run when you apply +12V to the grey wire located behind the alternator? Does the car start?No prime sound from pump pressure is just for a sec then drop to o
New 60 injector new filter new regulator n pump last year .n yes on second turn key psi up 45 then instant drop to zeroAt least you have a fuel pressure gauge to help diagnose the issue. Does the gauge do a slow gradual fall to 0 or is it truly instant? Once it goes back to zero , if you turned the key off and back on will the pressure jump back up to 45? I would start at the fuel pump also and make sure that every thing there is OK. If it is a common pump see if you can borrow ( someone's spare) or purchase another depending on age, parts do wear. Same goes for your injectors, send them to chuck leeper. ( Cody Motorsports) for a good clean and position reference to rule them out of the issue. Don't forget about the fuel filter and depending on the fuel pressure regulator the diaphragm can fail ( some can be rebuilt).
Fuel pump
Fuel filter
Fuel injectors
Fuel pressure regulator
Consider it spring cleaning of your fuel system.