I had vapor lock problems on a vehicle with similar bolt together Carter pump. It happened a short time after purchasing a new pump. I took it apart, and found the check valve disks were loose in the housing. The valves should have been press fit, but they fell out when I flipped the housing over. It looked like an adhesive was used in manufacturing. Very few adhesives work with modern fuel. I returned to store, the replacement worked fine.
It would get enough fuel to carb when cool, but not when hot.