I believe that the problem is with the fuel. If your tank of fuel is old and low, the ethanol could have separated from the gasoline. There have been reports of higher than 10% causing major damage. Modern cars with there fuel injection raise the boiling point of today's fuel so they don't have vapor lock problems. In our old cars today's fuel will boil at 100 degrees.

I have a post on adding a fuel return line to fight vapor lock, Lots of good advice.

https://board.moparts.org/ubbthreads/showflat.php?Number=6209669&page=0