what do you mean "9v draw"? the voltage anywhere in the system (referenced to ground) should be about 12v when the truck is off, 14.4 when the engine is running. There shouldnt be 9v anywhere because the voltage is set by the battery / alternator. current is "drawn" by the loads on the system. the only time the voltage should drop that much is when a large load is driven like the starter, or when the battery is heavily discharged. Sorry, end of electrical lesson...
What did you measure where you found 9v?
do you have a charging system message?
I would look for a light that remains on when the truck is off, maybe due to a broken switch. Like a glove box light or something.
Here is what i would do to trouble shoot...
1) from a charged battery. shut the truck off and close the doors.
2) Get a multi-meter that has a fused amp meter. most are only fused at 3 , 5, or 10 amps.
3) Remove one fuse at a time and put the multimeter in place of the fuse. the meter should read near 0 amps for all circuts. if you find one with a current on it, that would be your suspect system, then you can look at all the loads on that circuit and see which are on. Note, you cant do this with the fuse in place.
4) Since the battery takes all night to drain, its probably a small load so it shouldnt hut the meter, plus thats why the meter needs to be fused.
5) if you put the meter in and you see a high current (greater than 10 am or so) remove the meter and you may not blow its fuse.
Good luck PM if you want more details.