Car wont start

ok..both my 84 rocco and 83 gti did this...both cars sat a while and i couldnt get them to start. so i sat around moping for a few and i came up with this idea to see what was up. when i hooked the fuel pump up to the battery it started right up(the 83 runs sweet) and the rocco bogs out when i nail it....but screw that i dont want to rig up my fuel pump to an on/switch. what could i look for to see where the problem is.
i already checked the relays......any ideas?