I have often seen water droplets on the fuselage/wings of combat models, mixed in with the traditional black diesel sludge - usually only in typical British combat weather though! Could be from the ambient air, but the same conditions will prevail inside a tinplate tank.
Anyway, why would you want to use muffler pressure on a diesel? Fuel draw is the last of your problems with such small venturis.
Of course, Dave Day goes as far as to question how anyone can pressurise something with a big hole in the back of it