I don’t think so. I think my car pre-dates the sock.

Is there a "sock" on the fuel pickup in your tank? I've seen them get plugged up before and cause fuel starvation.

"FREE SAMPLE"

Thank you Ted. I did blow compressed air backward through the fuel line from the pump, and I heard strong bubbling in the tank immediately. That is to say, if there was/is an obstruction there was no delay in clearing it, at least temporarily. In any case, I think the next logical thing is to check out the line from the fuel tank.

I had a ’68 Cougar that had a series of fuel pump failures in a short period of time.  The pumps would simply fail to pick up fuel from the tank.  In some of the instances when the engine quit, the fuel line could be reverse blown back to the tank and that would fix the problem for the short term.  But the problem would continue on for several months with several pumps simply failing from what ended up being a problem with the fuel line from the tank to the pump.  The steel line had a natural trap built into it due to having to run around various bends in the frame that caught debris and rust from the tank and that unwanted material would simply plug up the line where it had to make an uphill transition.  Blowing the line backwards would temporarily clear the obstruction but because there were too many bends in that line, the debris was not getting cleared out regardless of the line being blown out from front to rear or rear to front.  Eventually found the problem with the line and simply replaced that section which cured the problem.

Lorena, Texas (South of Waco)

Thanks Ted. With my old fuel pump, which was on the engine for decades, the pressure in the fuel rail would evaporate virtually immediately. There was also a very consistent wavering of the fuel pressure when running, almost like a very quick windshield wiper action, between 3 and 4 lb, as shown by the inline gauge. This would seem to indicate to me some kind of consistent inefficiency in the pump’s action. Yet it performed well under all load conditions—only replaced it due to the oil leak.

At a steady state rpm, the fuel pressure is expected to be constant.  Under a load versus idle conditions, the fuel pressure will be less simply due to the engine taking in more fuel.
 
It’s not unusual for the line from the fuel pump to the carb to remain under pressure for extended periods of time after stopping the engine.  I would be concerned if it did not stay under pressure for awhile after shutting off the engine as that would be an indicator of a poor needle seat in the carburetor or weak check valve at the fuel pump.

Lorena, Texas (South of Waco)

Is some fluctuation in the fuel rail normal? Mine varies depending upon load.

Is it.normal to retain pressure after shutdown for a few hours? And if engine is hot at shutdown, for pressure to rise slightly, like 1 - 2 lb?

do any of these symptoms point to some kind of flow obstruction?

Thank you gentlemen. I guess my next step will be to access the tank and check forgunk.

Couple questions.
Is some fluctuation of pressure in the fuel line outlet normal? Mine varies between 1 - 5 psi depending on rpm.

Is it normal to retain pressure after shutdown, even for a couple hours? And if engine is hot at shutdown for pressure to rise slightly, maybe 1 - 2 psi for awhile?

FWIW. My 55 has an access plate in the trunk to allow removing the fuel gauge sender and you can look in the tank. Exercise caution, it's full of fumes. My bird had a handful of raffle tickets in it. 1/4 tank or less they cut the fuel off. No telling what you might find. I also replaced the hard line from the tank forward. We had to cut and splice it in front of the rear wheel on the outside of the frame. If there's a way to replace it with the body on the frame I never figured it out. That was on a hoist with nothing in the way.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

I had that happen on a '53 I had. It would sometimes run out of gas with a full tank; drove me bat shit crazy. After replacing everything in the fuel system except the carb and tank I pulled the the fuel sender and had a look inside with a bore scope. I found the culprit was a seal from a bottle of additive a previous owner must have dropped in accidentally. It would make it's way to the tank outlet and stop fuel flow. I managed to get it out with a shop vac and never had another problem.