Classic/Antique Car Repair: 63 FAIRLANE 500, mechanical fuel pumps, mechanic work

Question
( engine 289 )no gas to carb..... i have replaced fuel pump, fuel lines to tank, taken gas tank off and checked.. every thing is clean.hooked a hose to fuel pump and ran out of a 5 gallon gas can.. engine runs fine..  then hooked hose to hose going to tank...car ran find.... took tank off
checked fuel line going to tank everything clean... GAS WILL NOT COME OUT OF TANK.. I HAVE 5 GALLONS GAS IN TANK. SHOULD I FILL TANK UP ? also should gas be flowing out of fuel line to fuel pump.. i have been doing mechanic work for over 30 years this car has me stumped.. please help.

Answer
Time to get your vacuum gage out. Disconnect the inlet line from the tank at the fuel pump. Install your vacuum gage at the pump and crank the engine. You should see about 11 inches of vacuum at the pump. If it is way lower then the pump is weak. Next reconnect the line and break the line at the tank. Install the gage on the line and crank the engine again. The vacuum should be the same as it was at the pump. Mechanical fuel pumps are pullers and draw fuel from the tank by vacuum. If the vacuum is low it indicates a leak in the fuel line between the pump and the tank. If the leak is up over the rear axle it will not leak gas on the ground but will break the vacuum and not draw fuel. If there is vacuum and still no fuel the problem is inside the tank.
Brad