from a pacifica forum.....
take a pair of jumper cables and connect from the negative battery terminal to the engine block. use both the black and the red cables (more connection). this should work, temporarily, and then you will know your negative wire is no good. happened to me and several others.
the fix is a good sized wire directly from negative terminal to one of the starter bolts. (i used a 4 gauge) it starts like it never started before.