Are you saying you checked the wires leading to the tank (in the trunk?)and found none of them supplying power? But then after jiggling those wires the pump began to run? At that point did you check the four wires again? Perhaps you missed the 12v when you check the wires initially.

Another route to take is to supply 12v to the wire that powers the intank pump and see if the pump runs. If it does not run double check your ground. I have run into that fault several times- 12v was there but no ground was being supplied to take advantage of it. The grounds suffer from exposure to the elements on the top of the tank (if that is where your ground is).

Randy