[Old Henry]

If it is heat at the fuel pump causing the problem we call it "vapor lock" here in the states meaning that the fuel in the pump vaporizes and won't pump. Mine does that after sitting in the hot sun for 20 minutes after driving in the hot sun and the engine real hot. I can get it going again by pouring water on the fuel pump but I'm installing an electric fuel pump back by the gas tank to "prime" the mechanical stock pump when I have that problem in the future.

As G.M. said, try cooling the fuel pump with ice or water when you have a problem. If that fixes it then you know you need to put the electric fuel pump back in. You don't need to replace the mechanical stock pump you have, just put the electric pump in the fuel line back by the gas tank so it won't overheat and have the same problem as the mechanical one. Then just use it momentarily to "prime" your stock mechanical pump when needed rather than running it all of the time.