I bled all the injectors but a mechanic told me often just one will get things going. Even a gas car might not restart on one gallon. And diesel smells so nice as it lingers. SFI remember cracking all the fuel lines on an old tractor after running it dry. That was a pain. I've fuel starved a modern diesel once when it was crazy cold and it gelled but that obviously didn't introduce air so when it warmed up it was fine. I can't imagine this truck will be happy. Hell, dumping in 5 gallons may not even be enough to get the pickup fully submerged so you may not even be making progress when you start cranking.