I think I will start my first thread. I posted this on another thread, got no opinions.
OK, question here.
Consider an air leak in the fuel line on the input side of the pump, or as d.boat says, in the incoming oil line (or cap). The fuel pump will pull air into the fuel, and pump it through the system, up to the carbs, through the needle and seat, and into the carb bowls. Right?
The carb bowls are vented to the atmosphere. Evidence of that is the flooding over of gas if the needle sticks open.
So, why doesn't the air pulled in by a leak simply rise to the top of the gas in the bowl and rejoin the atmosphere? How can air possibly be sucked through the high speed jet (bottom of bowl)?
Now consider a leak on the output side of the fuel pump. I say there is NO WAY for air to enter the system there, because the fuel in the lines between the pump and carbs is under 3-7 PSI pressure. The only thing that would happen in this example is a fuel leak out of the system.