Chromeshadow

I agree with Dawson, sounds like the next thing to check is the ground. Does the pump ground through a wire or the case? I'd run a wire from the battery negative directly to the pump ground. I sometimes use jumper cables from the battery to near my test points, then small jumpers to the device I'm testing.
btw, if you get weird voltage measurements, you might want to double check where you clip your ground meter lead.

9550

If anybody thinks they know what the click I hear is, feel free to share