Been driving a Scania the last few weeks, its one of those ones with a tank on either side… Theres a sticker on one of the tanks that says full other tank first, Whats this all about, before i noticed it i was always filling the wrong one first, but it never made any difference and no harm has been done so it must be ok to full the wrong one first, it must be someting to do with the pump or somthyiing or maybe there is one tank that empties first and they work indepentinley or something… My Dad used to have an old Jag that had two fuel tanks (there different now i believe) but to change from one tank to the other you had to push a button as one tank emptied first… Trucks are obviously different and more technical nowadays…
They say fill a certain tank first because you can get a pressure build up in one tank causing the other/ or it to literally start overfilling it self from the other. Best way is to fill up but don’t put fuel caps on till both tanks are done/ or if filling one tank undo other side so pressure don’t build up. Just glad you did not get this problem, because when you see fuel coming out of the offending tank and you take the fuel cap off to take a look, you get literally sprayed with diesel and a good amount is dripping down your fuel tanks and on the ground. ( from experience )
Crikey i never thought that would happen, best be careful from now on!!!
always fill the tank up with the sender unit on first, as this is the source of fuel for the engine 
jimmy2loads:
always fill the tank up with the sender unit on first, as this is the source of fuel for the engine
Mine still uses coal!
i wish i could afford the coal to make mine run
globby 480:
i wish i could afford the coal to make mine run
also if both tanks are all most empty and you fill the big one first some times it will not bleed over to the smll one which feeds the engine.
I don’t think it matters if you are going to fill both tanks before starting the engine again but let’s say you are nearly empty and you can only fill one side for some reason, you need to fill the tank indicated to fill first as if you fill the other one, air can get in to the fuel pipes and disable it or some such. I think even at a push if you only filled the wrong one up and left the other empty there’s only a possibility of it happening but best not to tempt fate.
this post just reminds me just how backwards scanias are , most manufacturers seem to manage to get a decent size fuel tank on one side of the unit , but not scania , is this what i have to look forward to in a couple of years time when my volvo is replaced ? having to pass a fuel nozzle over the chassis & than a walk all the way round ? 
thats progress is it 
You could be worse off, you could have a Skoda like mine, one poxy 250ltr tank, consantly looking for fuel, why people rave about Skodas is beyond me, crap auto gearbox, fairy liquid bottle for a fuel tank, seats you have to fold forward to make a proper sized bunk, sorry rant over! 
dowahdiddyman:
You could be worse off, you could have a Skoda like mine, one poxy 250ltr tank, consantly looking for fuel, why people rave about Skodas is beyond me, crap auto gearbox, fairy liquid bottle for a fuel tank, seats you have to fold forward to make a proper sized bunk, sorry rant over!
WTF is a Skoda in trucks?
Scanias ,the Skodas of the truck world!
I fill mineup at the same time, because I have a body in the way I can’t drag the hose across so I only generally stop at places where both tanks can be filled together.
8wheels:
I fill mineup at the same time, because I have a body in the way I can’t drag the hose across so I only generally stop at places where both tanks can be filled together.
Try pushing the hose underneath the truck, it worked for me 
the tank with the fuel sender needs to filled 1st because if you fill the other tank 1st the pipe that runs underneath to the feeder tank can get air in it and then the fuel will not run across to the feeder tank, which wil end in you having used 1 tank of fuel and havin the other tank still full
thats what i was told by a lad who worked at scania