1991 fuel system problems

My niece has a 91 prizm. She lost the gas cap and has been driving like that for a few months. Her tank was full of junk and it plugged up her fuel pump and and injectors. We removed the tank and cleaned it, replaced the pump and filters, blew out the lines and put it back together. Now, we cannot get any fuel from the tank. Is there any way to confirm the new pump is working properly, without removing the tank again? We get fuel to seep out, but not anything more. Please help.