The 777 checklist is only entitled FUEL LEAK.
We are considering very different cases with regard to an Engine Fuel leak and a fuel leak elsewhere (tank, line, pump etc).
The checklist actually assumes an ENGINE fuel leak, but sadly doesn't state that in either the Electronic checklist (ECL) or in the paper QRH.
Sadly in the case of a fuel leak not in the engine, blindly following the checklist may lead to problems.
It advises to shut the engine on the affected side down in the assumption that that will stop the leak.
It then advises that normal fuel balancing can be actioned. Not a great idea if shutting the engine down didn't solve the problem. You will now be in the position of pumping useable fuel from the good tank across to the other side and overboard. oops!
So there you are, mid atlantic, engine shut down, leaking fuel out of both tanks!! Doh!!
Consider the Airbus that managed to glide into the Azores. They were lucky...
PS TOP TIP - When the Fuel Imbalance message is displayed after an engine failure don;t just assume its due to an engine being shut down. Do make a positove immediate check as to whether you have developed a leak (a la Concorde). A quick look of Calculated vs Totaliser on progress page 2 gives a quick confidence check.
happy flying.
Rgds,
SR