raul.garcia

New Holley 255 LPH in-tank fuel pump, and new Holley adjustable fuel pressure regulator.

Pressure comes up to 44psi and holds until primer relay de-energies, then bleeds down to 0 psi

Pressure gauge indicator needle bounces rapidly from 30 to 40 psi while engine is idling.

Fule pump is really loud can be heard above exhaust note.

Can these two problems be related?

Thanks, guys for any input.

TheGreatJ

Sounds like a leaky regulator or injector. The fuel pressure should stay up after the prime pulse ends if the engine is not running. Get a pair of pliers and pinch off the return line, then hold it shut while a friend turns the key on. If the pressure stays up after the pulse, it's definitely the regulator. If the pressure still bleeds off, you may have a leaky injector or possibly a bad pump that won't hold pressure. Does the car run rough or blow a cloud of black smoke at startup? Those would indicate a leaky injector.

Zepher

Does it take a few cranks before it starts up as well?