4051 Channel Isolation

Hello,
I am trying to figure out what is going on with a 4051 Multiplexer that is giving me issues.
I have a + Power, a + Sensor, a - Power, and a - Sensor running into 4 channels of the 4051.
It seems to me that I am getting a connection between the + Power and the - Wires.
I would have assumed that the channels of the 4051 were isolated from each other, but this does not seem to be the case.
Is there a way to isolate the channels of the 4051? If not, do you know if there is a Multiplexer that has isolated channels?
Perhaps I am just completely misunderstanding what is going on!
Thanks!

do you have a link to the datasheet of the 4051?

Sensors must have common grounds and must be connected to the Arduino ground.
See image:

Edit Added GNDs

2014-12-14_13-28-56.jpg

CD4051 Datasheet

Don't allow the 4051 control lines to float or you may get erratic operation. I've used a high value resistor to ground on the control lines to make sure they don't float when not made high.