[sammyg2]

I just re-read your post:
One thing to add. If you have a large suction pipe with huge volume, it would take the pump longer to take suction because it would have to displace more air to create sufficient vacuum to take suction.
It would not be harder from a load standpoint, just take longer. During the time it was developing sufficient suction it would be trying to pump air and not be running in liquid so it wouldn't be lubricated or cooled as well and in extreme cases that would lead to premature failure, if that what you meant?

Not to muddy the waters any more but most in-tank pumps don't lose prime so they don't have to re-establish it every time they are turned on. That is usually due to them having a foot valve (a check valve at the suction screen to keep the suction line full at all times), or possibly I suppose in some applications it could be designed to take advantage of the drinking straw thing we discussed earlier. Problem is, most fuels don't have a very high surface tension when compared to water and would lose prime after a while unless the suction line was teeny tiny (technical jargon).