The leakage from a ruptured fuel pump diaphram will occur mainly when the engine is running,,,what ever pressure is left over between the pump and the carb will bleed off slowly,,,,how much fuel are we talking about here?? (knowing that no amount of fuel in the oil is a good thing),,,mechanical fuel pumps can go to 14lbs when they are in good condition,,,the pressure is only regulated when the motor is running via your fuel bowl floats and needles.
When the engine is off there would have to be quite a bit of pressure in the tank to push the fuel past the diaphram.
You can run a test for yourself by disconnecting the fuel line supply to the carb and have it run into a glass mason jar,,then turn your motor over with the key,,then observe the fuel coming into the mason jar,,,if you see lots of air bubbles (airiated fuel) then you probably have a cracked diaphram.