Fuel tank not equivalent. Can anyone help?

Did you replace BOTH vent valves? (Assuming 1 for each tank..... dont have a freightliner but each tank on my vulva has it's own breather filter)

If you crack the caps and run like that for a while, will they equalize?

 

If you are running and you go to pull the caps off are either of the tanks under a vacuum?

 

I have found that if the tanks are venting properly and one tank is staying full or gaining fuel while the other goes down that the tank with the abundance of fuel has a blockage on the suction side of that tank. I would get fuel tank low and suck out as much fuel as possible then with cap off remove the suction line on that tank and blow back into it. I have found anything from oil caps, panty hose, tire thumpers straps, plastic food wrappers in them. Sometimes it is difficult to find the item.

 

Are Freightliner tanks like Peterbilt with those metal pipes that go to the bottom of the tank?

 

F/liners have the fuel tube starting at top and stop at a few in. from bott. and both return lines run to equal valve that is mounted on rear of trans and when you have one tank full and other near empty, ck for blockage then replace the Equaliser valve while its fuel lines are off blow everything you can into a bucket under truck ck. for plastic bags and other things that can block off fuel?