There are early fuel pumps that have just the contact points, no
electronics. On later cars, a diode was added to help prevent point
arcing. the direction of the diode is determined by positive or
negative ground. So early pumps didn't matter, but later ones did. If
you removed a diode, it would work regardless of the grounding, but
there would be more arcing.
The addition of a transistor circuit, using the points for low
volt/current switching only, also makes it dependent on polarity.
Brad Fornal wrote:
>I notice they sell positive and negative fuel pumps, but why???