1. you need to stuff more of the foam from the box under the pickups.
2. unless the pickup is itself damaged or the pots are bad, you by definition did not wire it like the diagram. you just gotta re-check everything.
try the "noise trace" test; open up the bass, plug it in and crank it. if you touch the tip of the cable (while not touching anything grounded) you should hear a loud buzz. from there, go to the next stop of the hot connection, the output of the volume pot, and touch that;
keep going up the trail towards the pickup hot itself, where it connects to the bobbin; the place where you don't hear buzz is the place where the failure is happening.
(now if you plug it in and hear no noise when you touch the tip of the plug, then you have a short, from hot to ground. look for a solder blob or stray wire or pot lug touching something it shouldn't.)
Guitar Repair Gnome
Alpha Music, VA Beach