gas leak after inigition is off

[bsharp]

Need some help--1978 fiat 124--turned my engine off at night including fuel pump -woke up next morning and gas was leaking out off carb on to ground- must have been 0n all night--must have filled up at least one cylinder-would not turn over by starter-used wrench an inch at a time to turn engine-finally got it to turn over by starter and at least a half gal of gas spewed out the top of the carb--Opened the gas tank cap and a whole bunch of pressure came out.. anyone know why the gas would keep running out of the tank into the engine without the fuel pump being on

[So Cal Mark]

pressure in the tank, it should be vented to evap cannister