Right tank keeps filling up! HELP

If both return lines are clear, then see if the fuel lines or return lines are different lengths from one tank to the other. If there is a big difference, the shorter hoses will draw faster.

 

You should still have something that goes tank to tank.
No fuel system I have seen is designed to where the fuel has no way for gravity to equalize it.
They can clog inside the tank as well. From junk settling on the bottom.

 

My '07 Volvo 780 does NOT have a crossover. The only way the fuel tanks can equalize is from the fuel being returned from the engine by decisions of the proportioning valve. When the engine is off then the valve must open allowing them to balance as well.

 

I've never had it over fill the other tank before but I have had trucks that draws fuel unevenly. Top off, one will get down to 1/4 but the other one will be up at 3/4 full.

 

Had the same thing happen on an 05 Shaker. Proportioning valve went bad. Ran me out of fuel on Tiger pass, on the passenger side tank (hwy 18 WA, no shoulder). Made for a nice traffic jam. Since the fuel gauge read the drivers tank, it said full.

 

Freightliner??? Just for grinns...look under the drivers door and above the fuel tank and see if there are two yellow handles there.....yes? Push them in... hard. No?...no idea...

These are great for pulling pranks on your fellow driver.