if it won't start again, unless you pump the gas, it sounds like it is running out of fuel. Was this carb new to you or have you had it on an engine and had it running? It does almost sound like there is a vacuum leak, some Holley's have a vacuum port on the pass side under the front float bowl. Also, dis you check the screw in the bottom of the carb that hold the main body onto the base plate? They can come loose and cause vacuum leaks.