You mean a new Nitrile diaphragm in the fuel pump?
Yes, unless you want to have one put in mine😉
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When it dies, jump out and open the gas cap. Is there a sudden large intake of air?
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Good to try. Plugged vent cap?
My first ethanol problem was an old commercial truck that would start up and run fine until accelerating hard. It would begin to surge and holding the accelerator to the floor would result in the engine stalling. That truck’s rubber fuel line at the tank was not leaking fuel but it was porous enough to allow air to be drawn in and bubbles won’t pull fuel through the line up to the engine. I can imagine that on an incline the T-bird might have the same problem. I didn’t recognize that ethanol was the likely cause of my problem for a few years.
Well, whatever the problem is, it’s really bad now. I cant even get enough fuel delivery to fill the bowl. It won’t run at all. Vent cap is fine. Checked that 3 times. It won’t even idle now. I ordered a new Holley 4160. I’ll have it tomorrow. Line between the tank and the fuel pump has been checked and rechecked. 2 new fuel pumps. new gas tank, new sender and pickup tube. Im hoping they screwed up the rebuild on that carb because I just am running out of things to check and replace. Of all the vintage cars Ive had…all the thunderbirds, corvettes etc etc, this one is kicking my butt. By the way Rod_Knox there is no rubber fuel line on this car except from the metal line to the fuel pump. Its about 9" long and its brand new. Ive checked it twice, but your symptoms are the same as mine. Seems like the fuel pump is losing it’s prime like a broken straw. I just cant find it.
Remove the fuel pump and check to see if the eccentric in properly mounted on the camshaft gear. Next place the fuel pump in a vise, see if there is suction on the inlet while actuating the lever. Some fuel pumps have a screen in the inlet to catch debris, I have seen these pug up with rust particles.
I found the problem on that old truck by injecting ~2psi air pressure into the tank. The bad hose became damp.But that test would pinpoint any leak including metal joints.
What about switching to an electric fuel pump?
I just remembered. I had a similar problem on my 1978 Oldsmobile Cutlass. It had a mechanical fuel pump. I couldn’t get it to run well enough to get it out of the driveway. I had it towed to an old time mechanic. He found the problem was a deteriorated flex hose at the gas tank. It was an inexpensive repair, but it had me baffled. The car ran beautifully after the repair.