Tabetha that's cojones.

Voltage drop / series resistance is going to be MUCH greater down any size cable compared to a great chunk of steel. So long as care is taken to get good contact with bare metal over a large enough area (i.e. same size as terminals on pump), and protect it, then your point is moot.

I would be more worried about protecting another large diameter cable for the length of the car to be honest!