I'd say that, looking at this thread, you have a loose coupling in your fuel line somewhere. This may have been caused by presumably disconnecting and reconnecting the lines when the fuel was drained or it may be that the petrol has eroded a gasket / seal.
I'd suggest following the advice in the penultimate post of the link I've posted, namely...
isolate flow and return fuel lines from the tank. fit pressure gauge to system and manually pressurize. if system does not holding constant pressure for 10-15mins, carefully work your way along the fuel lines to find culprit and replace. it may be something as simple as a union needing tightening up. pay attention to the injectors and injector rail, and any flexible fuel lines.