Hi people,this is my first post as l am a new member.....my L400 suffers from fuel draining/syphoning back into the tank after standing for a while,usually overnight,it didnt used to do this,but now l need to prime the fuel line to start it,then operate the priming pump for about a minute after which it will be fine all day....l am considering a one way valve in the 8mm feed line where it leaves the tank,anyone have any thoughts??....l have the tank out at the moment and am fitting new fuel hoses,but l am confused by the two fittings on top of the tank,connected by a 6mm bore hose with what appears to be a one way valve plumbed in....it has a direction of flow arrow on it but l can blow through in both directions,seems a bit pointless really!!!,any help appreciated,my deli is a 1994/5 L400 super exceed 2.8 diesel 4m40 engine