As the others have said, it's more than likely the nipple and not the line. It's very very very common for the nipple to crack. I would say half of the sending units on the cars i get in are cracked on 2002 and up. I've never seen a cracked line. The line would be a ******************** to replace as I believe the front suspension and tank need to come down so you have access.
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Woody
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