[turbo6bar]

Suction head for a pump is expressed in feet. Never mentions anything about pipe diameter. I think the only time the pump would suffer is during priming. The pump would have to lift more water with a larger pipe and would take longer to start pumping. If the pump isn't self-priming, I think you could have issues.

FWIW, I finally went to a mechanical fuel pump driven by the crankshaft on my Dodge.It and a Racor heated filter are my current favorite. The Racor heater has allowed biodiesel to be run later in the season without power loss.