So basically, the pumps don't want to fill in the train. Try and error in map editor reveals, the pumps work, when i put fluid in the train manually... so how do i do this in a normal game?

Thanks for the report. Apparently a factorio update changed the way fluid mixing is handled. Previously fluid systems were locked into a single fluid type. This was used to determine what pumps the train connects to when it is empty. After this change the fluids are no longer locked in and therefore this mod has issues determining what pumps a locomotive should use. It therefore does not connect and will not refuel.

TL;DR: Factorio Update broke this mod. Will attempt to deliver a fix soon.

i just pushed an experimental fix (version 0.18.7). It will now again connect, but only if the pumps have fluid in them.

Thanks a lot! I will test it later on!

It works now, thanks a lot!