After all these years I still can't get water to drain uphill after the spring melt. I should put a carb in the low spot on my yard because according to so many guys carbs are great at getting liquids to reverse the affects of gravity!
Kidding aside, at first glance to a lot of people it seems like the fuel is draining back when the problem is in fact evaporation. Ever put a jerry can of fuel in your trunk on a hot day? Come back later on and it's blown up like a balloon from, imagine what happens in your carb where the bowl vents are open to atmosphere.
Agree the pump is likely fine... especially if it runs OK after starting. Fuel evaporation is very likely. I have switched my carb vehicles to electric pump for this reason. Key on for a few seconds re-primes the system and starts right up. This also can eliminate vapor lock.
Same here. I can't think of any good reason to mess around with a mechanical pump these days.