Q-Jet Problems

Ok I have tried just about everything on this q-jet but still can't get it to work. Here is the problem. The bowl fills up no problem but fuel will not pump out of the carb. Even when I push down on the pump manually it will not spray. The acc pump is brand new and the carb was rebuilt not to long ago. Here is the strange thing, if I pop the top off the carb and press the pump down, the fuel squirts out of the hole. With the top on, no fuel comes out. If I dump some fuel into the carb the car will run for a sec so I know everything else is set up correctly. This is a 1974 q-jet for a vette. I installed a new gas tank, filters and fuel line. I also installed a holley mechanical fuel pump rated at 7.5 psi. There does not seem to be any vacum leaks either. Any one have any thoughts?

one of 2 things are happening ,#1 the accel. pump passages in the top of the carb are clogged in wich ya just pull the top of the carb & clean/blow out all the passages.or the gasket is interfering with those passages.......
#2 and the most likely is the accel.pump check ball was left out during the rebuild........

some info.............
http://www.tocmp.com/manuals/Carbs/Rochester/QJet

Thanks guys, got the carb running. I thought I had it all cleaned out but one last cleaning must have done it. Thanks again for everyones help!