Dave:
Did I say some "ham fisted jerk" over torqued the fuel injector line!
! Of course, I was not referring to you since obviously you were trying to correct someone else's mistake!!
Ron offers some very good info. The dreaded algae/bacteria gremlin can cause all kinds of problems with the fuel system. Usually, the fuel filters catch most/all of the algae before it gets to the more delicate parts of the injection system. But, I have read about some cases where algae ruined other parts beyond the fuel filters. Ron has had an unfortunate personal experience with these gremlins that all of us would like to avoid like the plague!! See the recent post in the Diesel Forum about algae in diesel fuel and the various replies in that post have links to more very good info.
Larry Bible also provided very good advice and finishes off what I should have said - inspect the lines by taking them off (of course that is the only way to see if the ends are deformed, smashed, nicked, cracked, etc.).
Good Luck!
Tom