Fuel system question.

[Colban]

Year 2000 1150/ABS.
Just replaced my std 21L tank with Adv 30L.Connected fuel lines to distribution manifold as i thought they should be.Bike would not start.
Switched fuel lines around at the manifold-now starts.
I thought that the manifold was simply pressurised,with the relief valve allowing fuel back into the tank and that it did not matter which way round the pipes are connected;but is it the case that the pressure relief valve acts as a one way valve as well?.

 

[Steptoe]

It has to work only one way to maintain pressure.

One pipe is a supply, the other a return. If attached the opposite way around the pressure valve is forced closed = no fuel , hence the non starting.

Thats why the bikes with quick release couplings have them fitted so you can't mix them up.