Hi guys, ive got a problem with the N/S fuel tank on ‘my’ Scania. Basically another driver at work used it and filled up the N/S tank first and now it only uses diesel from the O/S and doesn’t filter through or burn the diesel evenly, Every driver at work is a mechanic and all I need to do is just turn a tap underneath the tank and it should go through, I have actually seen the said tap but just looking for a second opinion really. Cheers.
It could also be the breather tubes on the tank, if they block up the syphoning from one tank to the other can’t happen, other than that, try the tap as suggested by the ‘experts’ 
If the tap is off turn it on
If thr tap is on leave it on
If you’ve got an airline in the cab grab a rag put it over the filler neck and fill the secondary tank with air. Sounds like you’ve an airlock and this is one way to solve it.
switchlogic:
If you’ve got an airline in the cab grab a rag put it over the filler neck and fill the secondary tank with air. Sounds like you’ve an airlock and this is one way to solve it.
This ^^^^^
I had a twin tank Scanny and used to fill either or the other first and they’d always balance off.
I once run out of fuel on the M25 in a different twin tank motor, I knew that there was plenty in the tank and was only a few miles from J21 where I’d planned on getting fuel. Once we got it sorted I went and filled both tanks to the top and calculated that I still had about 130 litres but was draining the fuel quicker than it could balance off.
Adjusting the taps underneath got the tanks to balance off, weird as it’d never been a problem before. Apparently according to Scania service they get a run on this where people have been closing the taps overnight.
Tie a knot in nearside breather pipe and make sure both tank taps turned on.With nearside beather pipe knotted should draw from that tank first or use at same level .atahsts all I have done on my R500.
Thanks for the quick replies fellas, I will try all of what has been suggest 
you need to make sure BOTH taps are open.
The reason it does not filter through is because it is set up to allow you to fill one tank at a time, if fuel flowed through easily every time you filled up filling one side at a time would mean when you went to the other tank it would be half full and so would the tank you just filled. Just fill both tanks to tthe brim and leave the taps alone, they will then drain to the injection system evenly.
Do NOT pressurise a fuel tank with an air line. Repeat do NOT do it. A fuel tank is not a constructed to withstand 100 plus psi. It may well explode. Yes, many fitters do it, just like some try welding a sump on the vehicle or a fuel tank off it. Not all have lived to tell the tale!
cav551:
Do NOT pressurise a fuel tank with an air line. Repeat do NOT do it. A fuel tank is not a constructed to withstand 100 plus psi. It may well explode. Yes, many fitters do it, just like some try welding a sump on the vehicle or a fuel tank off it. Not all have lived to tell the tale!
dont panic, dont panic!.. i dont think anyone is saying put 100 psi in the tank, all you have to do is use your brains and put in enough air to force the fuel through!
Moose:
cav551:
Do NOT pressurise a fuel tank with an air line. Repeat do NOT do it. A fuel tank is not a constructed to withstand 100 plus psi. It may well explode. Yes, many fitters do it, just like some try welding a sump on the vehicle or a fuel tank off it. Not all have lived to tell the tale!dont panic, dont panic!.. i dont think anyone is saying put 100 psi in the tank, all you have to do is use your brains and put in enough air to force the fuel through!
Yes exactly, talk about scaremongering. You dont blow up a tyre till it explodes, so why would you a diesel tank. I’ve done thins several time.
FarnboroughBoy11:
Hi guys, ive got a problem with the N/S fuel tank on ‘my’ Scania. Basically another driver at work used it and filled up the N/S tank first and now it only uses diesel from the O/S and doesn’t filter through or burn the diesel evenly, Every driver at work is a mechanic and all I need to do is just turn a tap underneath the tank and it should go through, I have actually seen the said tap but just looking for a second opinion really. Cheers.
correct me if i’m wrong, but, isn’t there a sticker on the tanks stating that the N/S tank should be filled first?
Yes there is in several languages!
Our 4 series has a sticker on the (larger) O/S tank saying “fill the other tank first”.
As far as I know, dual tank vehicles still only draw fuel from one of them, in the case
of our Scania, the nearside (smaller)tank.
The DAF has an aftermarket additional offside fuel tank(smaller than the main tank) and is prone to not drawing from it
regardless of which one is filled first.
This can be easily resolved by simply wiping the end of the breather and blowing into the tank,
with the lid on, obviously.
Although there isn’t much pressure from my lungs, there is enough surface area to force
the diesel to start flowing.
I think, the general principal is to fill the tank that supplies the engine first, then the “extra”
one, regardless of which one is larger but I stand to be corrected.
Regards,
Nick
Quote from NCOOPER
“This can be easily resolved by simply wiping the end of the breather and blowing into the tank,
with the lid on, obviously.
Although there isn’t much pressure from my lungs, there is enough surface area to force
the diesel to start flowing.”
Just how big is your mouth ■■? LOL
Trukkertone:
Quote from NCOOPER“This can be easily resolved by simply wiping the end of the breather and blowing into the tank,
with the lid on, obviously.
Although there isn’t much pressure from my lungs, there is enough surface area to force
the diesel to start flowing.”Just how big is your mouth ■■? LOL
just how big do you think the breather pipe is■■? 
shuttlespanker:
Trukkertone:
Quote from NCOOPER“This can be easily resolved by simply wiping the end of the breather and blowing into the tank,
with the lid on, obviously.
Although there isn’t much pressure from my lungs, there is enough surface area to force
the diesel to start flowing.”Just how big is your mouth ■■? LOL
just how big do you think the breather pipe is■■?
hang on while i get my glasses on and read the post properly
shuttlespanker:
FarnboroughBoy11:
Hi guys, ive got a problem with the N/S fuel tank on ‘my’ Scania. Basically another driver at work used it and filled up the N/S tank first and now it only uses diesel from the O/S and doesn’t filter through or burn the diesel evenly, Every driver at work is a mechanic and all I need to do is just turn a tap underneath the tank and it should go through, I have actually seen the said tap but just looking for a second opinion really. Cheers.correct me if i’m wrong, but, isn’t there a sticker on the tanks stating that the N/S tank should be filled first?
Yes your right there is on our other scanias but not on the one I drive, I have the square tanks 400 litres each I think they are but with no stickers or anything on them.