Observation I've made which makes me certain this is a bug: removing a locomotive at the back and adding it again will "start" the pumps (this seems to shift it the half-tile required to sync it; this may be related to viewtopic.php?f=7&t=73466 ?

In an effort to compact my base, and given that train stops cannot be set on a curve, In sandbox mode I created/came upon (it's not very revolutionary so it's probably been done before, but not by me) this system, which can fit an extra two wagons - allowing me to have a 4-8 train rather than a 4-6 ...