vauxhall vivaro van 04 wont start?

vauxhall vivaro van 2004 lost power but continued to drive next day wont start plenty of fuel injectors checked ok . no fuel coming into filter ,is the ecu at fault or the pump in the tank if there is one?. also leak of diesel from injector rail at small pipe that connects onto the end of the rail. DONT KNOW WHAT THIS PIPE IS FOR, I THINK THAT IT CONNECTS TO A VALVE AT THE END OFF THE INJECTOR RAIL.