yea, its getting plenty of juice, Ive tested it even at the starter..
but a weak starter? you may have somthing there.
is that a common thing for diesels?
i have a few but never had any problems, im a gas engien guy, and i had the starter in my 77 buick hears work untill 3 of the brushes wore past the holding screw and snapped off and the forth was never connected.