Come on guys, play nice, both repair and modify are both equally acceptable solutions to the problem.
lucky for me, my UR1 is gravity feed so i never get air sucking in..... just diesel leaking out a little but not bad enough to bother fixing......... yet.
My personal quick fix for a under mount tank UR1 would to be to fit an electric (facet or similar) low pressure lift pump as close as practical to the tank, switched on by the ignition..... this way you always have pressure at all the points that may otherwise suck air if there is a slight leak.
Personally i would not run any diesel (car truck tractor or otherwise) without a lift pump before the filter and injector pump......
and yet all late 80's and 90's Jap diesels with rotary pumps rely solely on the injector pump to suck diesel out of the tank and through the filters..... it is just stupid cost cutting at the factory and not in any way a good idea. in NZ when the low sulphur (and also low aromatic)diesel came out a few years ago pretty much every used diesel car on the road (mostly from the 80's and 90's) broke down due to previously happy but swollen seals, shrinking in the low aromatic
fuel, and if they sucked air in you got stranded...... if they had lift pumps you would see the pool of diesel on the ground but they would never have broken down at the traffic lights or half way up a hill.
I found out the hard way if this happens on a Nissan Vanette you can smash the high speed governor shuttle clean out the side of the pump.......... the reason is, it is a
hydraulic governor running in diesel, if there is air in the pump housing it over-through and bangs against the cover plate, until the 2 m6 bolts brake off and your wife is left stranded on the express way while you are out of town on business for two weeks 1000km away
this would not have happened had there had been a pressure feed to the injector pump!
As least the Zetors kind of have a remote lift pump, all be it in the injector pump housing, but not internally plumbed! so at least the filters are under pressure!
Yes, a little swirl of bubbles in the glass bowl is normal .... at least if the lift pump is doing it's job,
However nothing beats piece of mind, when it is a long walk home!!!!!!
and if that means some simple modifications to improve the factory system, then go for it.