Another fuel pump ?

[dart6]

This is a small block so it doesn't have the eccentric rod. The pump pumped fine before but not now so i replaced it with another new carter pump and the same story sometimes it pumps but mostly it doesn't, this is going directly from a gas can too. I'm wondering if i should just put an electric pump in

 

[dart6]

any thoughts on why it pumps intermitantly, is it the eccentric even though my search of the forum indicates the eccentric does not wear, or is this assumption wrong
Is there some sort of trick when installing the pump