If you have fuel pressure at the carb and an empty float bowl there are only the float level and needle valve to play with. If you have rubber line at the carb you can put one of those clear inline fuel filters at the carb this will give you a good idea of how much fuel is getting to that point. Look at the level when it is first running and then when it crashes. If the level is about the same in both cases you have a carb problem. The gas can't get to the float bowl. The float or the needle valve are sticking shut or trash. If the level is not about the same move the filter to the suction side of the pump. If the level is different here you have a blockage before that point. If it is about the same I would look at the pump. You could run rubber temporary lines just for the test. I guess there could be a pump problem that would cause the suction side fuel level to be different but this has worked for me.
