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Can someone please advise of the correct fuel pressure (PSI) from the fuel pump to the carburetor? Thanks

I don't know an EXACT value for yours. But 2-4 PSI is typical on most cars including Packards.

Why do you ask? Carb or accel pump not working?

Motors Manual 20th edition gives the range for 48-50 models as between 3 1/2 - 5 1/2 psi. Service Counselor issue Vol 22 #1 gives the factory spec for the 48 Custom 8 engine as 4 - 4 3/4 psi with a delivery of 1 pint in 45 seconds. What I have never seen mentioned with that 1 pint delivery spec is the speed the engine is supposed to be turning when measuring. Since the 22 - 23 series were for all practical purposes except trim placement identical, the 48 factory spec should be valid for your 49.

Wanted to know the fuel PSI because will be installing a Carter P4259 electric fuel pump to assist in getting started. Will also install a pressure regulator with gauge (plus filters and shut off valves). The electric pump will be activated by a momentary switch. Once the carburetor is primed by the electric pump, a bypass tube (with check valve) will be used to supply the mechanical pump.

Instead of a regulator, maybe just a check valve with an opening pressure of about 4 or 5 PSI with a return line to the tank would work better.

I'm not sure a regulator would work well with an incompressible fluid.

When I started finally working on my 1956 Clipper Custom I discovered it had an aftermarket fuel filter with a built in adjustable regulator and also my 1954 Patrician had a regulator in place of the fuel filter which I kept set at around 2.5 lbs. Both of my blogs show them.

I actually checked my mechanical pump pressure on my 23rd series 327 yesterday. Held steady at almost four psi at around 750 rpm.

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I just installed a freshly rebuilt fuel pump on my '49 with a 288. It was pumping out 5-6 psi. Took it for a drive and it stalled out after a bit (still trying to determine why - been chasing it), so I installed an inline regulator and dialed it back to 3-3.5 psi and drove it again. Same problem. Frustrating!

Monday, I am going to set up a direct feed to the pump from a clean can of gas, get it running, and try again. If the problem goes away, it MUST be somewhere in the pickup tube in the tank or in the long steel back-to-front fuel line.

This was probably asked already but have you checked the rubber hose to the pump? Even if they look good on the outside, sometimes they collapse internally causing fuel starvation.