Volvo 670 Fuel issues continue. Tanks will not level

Return fuel lines should be below fuel level all the time and air tight. So fuel will level in fuel tanks. Same principle as siphon working.Once it was open or lost air tightness because bad O-rings connector you need to push fuel from one tank to other with air pressure applied to the breather pipe.
Close the filling cap on one side and apply 15 psi. You need second guy looking inside the other side tank. Once fuel flow is clear no air bubbles you done. If it still lost leveling you have air sucking in return line.
Could be air or excessive gas from faulty injector, head cracks or fuel pump

 

I had this problem. Changed every line, junction, vents, fittings, left the caps cracked open...nothing worked. It always filled the left tank and I'd have to shut off the right tank to draw out of the left. Finally I took the line off at the tank and blew air into it and heard something blow out of the pick up tube. Turns out the lock from the cap had fallen off and got sucked part way up the tube enough to restrict flow but not stop it completely.

 

Hey buddy did you ever figure out what the issue was with your fuel leveling out in your Volvo 670? I'm having the same problem with mine. Ive spent over 6k trying to get this thing to level. If you were able to fix it PLEASE let me know..

 

What year is your truck and what engine??

 

I'm having the same problem with my volvo wg64t with a Cummins n14 to the point my passenger side tank is blowing fuel out the cap and driver side is almost empty. The lines on my truck are at the top rear end of the tank though. Please email me at lngfrancis2012@gmail.com