I just resolved a hard starting issue that was incredibly difficult to resolve and I want to share it with the hopes of helping others avoid my difficulties. 
I recently purchased my 1980 Pinto from a collector in California. It had been sitting in inside storage under a cover for 10 years when I bought it.  It started and ran fine when I picked it up. When I got it home and let it set for a couple of days it wouldn’t start without spraying starting fluid down the carb and this continued for the next 6 months. I finally decided to replace the carb to fix the problem. That did not work although once I got it running it did run better with the new carb so it wasn’t a total waste.  About the only other issue I had with the car was that the gas gauge didn’t work. I determined that the gauge worked by connecting the two wires where they connect to the sending unit on the tank with a wire which caused the gauge to show full. The only other thing it could be was the sending unit so I emptied the gas from the tank and removed it from the car. Once inside the tank I found the problem.  The brass float was 90% disintegrated but upon a bit of testing I found the gauge worked, it just need a new brass float and rubber seal which I found on eBay for less than $20.  One thing that I found inside the tank was a short 2 inch piece of 5/16 inch gas hose with what looked like an orifice that is attached to the return line from the fuel pump. It turned out to be a check valve and it was clogged and the gas hose was almost totally disintegrated. I cleaned out the check valve with carb cleaner and replaced the gas hose and put on the new float, reinstalled the sending unit with the new seal. I replaced the 2 10 inch pieces of gas hoses that lead to the metal fuel lines that lead to the front of the car. One is 1/4 inch and the other is 5/16 inch gas hoses. Once everything was put back together the engine fires right up no matter how long it sets between starting. I hope this helps someone save some time and money