Possible fuel selector issue

[netwalker]

At the start in LOWI both fuel tanks were filled with the same quantity. 
The fuel selector is set to Auto, the AUX BP is also set to Auto. 
After a longer flight the message "Fuel inbalance" appears.
The left fuel tank has 59 l, the right tank 127 l according to the display.
Even if I switch the fuel selector to the right tank, the fuel from the left tank will still be used.  
 

[Goran_M]

Check your fuel caps are secured.  It sounds like you were leaking fuel.  (Yes, we simulated that, and you can actually see fuel streaming out of the opening at an accurate rate)

Edited September 25, 2019 by Goran_M

[netwalker]

I close the fuel cap of the tanks every time, so an open fuel tank cannot be the explanation.
Even if a tank had remained open, why did the plane continue using  the almost empty left tank after switching to the right almost full tank ?

[Goran_M]

The selector will automatically switch at a predetermined time, regardless if the fuel cap is on or off.  

You might be surprised at how many people forget to replace the fuel caps after fueling.  If it isn't the fuel cap, then check the integrity of the airfame through the maintenance manager.  We've modelled wear and tear on the wing seams/joins, and fuel could be streaming out of the open/worn join (near the flap tracks).  

[netwalker]

Quote

You may be surprised how many people forgot to close the filler caps after refuelling.

No, sometimes  I forgot it at first myself, too, but  once after seeing the animated fuel leakage, I close the cap every time carefully.
Otherwise the fuel inbalance didn't come up during the next flights anymore. 
I checked the airframe integrity, but all was OK.