I just got a 73 Maverick with the 250 6cyl. engine. It has 23,000 original miles and had not been started since 1990. It fires and runs if gas is poured the down the carb. I put a new fuel pump and changed the rotted line from the pump to the metal line. It has at least 3 gallons of gas. It still will not pump, I pulled the new line loose and blew air backward to the tank thinking there was a clogged. I could here gas bubbling in the tank it started pouring out of the removed line. I quickly replaced it. I thought I finally had the pump primed and it would run. No success. I pulled the line at the carb before it gets to the filter. and cranked it several times and still no fuel. I was thinking the fuel pickup maybe clogged but blowing air backward and hearing gas slosh around in the tank, It may have cleaned the line but no. There no leaks
Try disconnecting the rubber line that runs from the body into the fuel pump under the hood in a small gas container and see will the car's pump suck it up enough to keep the car running or at minimum start it. I had the same issue, thought my pump on the side of the block set around and went bad but not the case. It will run off a gas jug but my tank was dripping and had cancer so it was sucking too much air ... I guess. Now if the metal line running down the body has any kind of gummy gas etc in it will prevent good enough flow until the car warms up to the running idle temps so maybe try blowing it out with carb cleaner & air compressor. If you do this then disconnect both sides !!!
