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uneven fuel return, 2010 kenworth t660, 450 ISX cummins

It started about a year ago. It holds a lot more fuel in the driver side tank, sometimes the difference is more than 40 gallons, but mostly 25 to 30. I have checked the vent tubes, and tried leaving the fuel caps just barely snug, to really tight, nothing seems to make a difference. Also if I stop for the night, it will cross over, and even out, once I start driving again, it moves back over to the driver side. Of course our shop manager thinks I am crazy, and says there is no way the fuel can do that when the truck is off, but it does! It leads me to have to fuel more frequently than I should have to. Any help would be appreciated.

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Check your fuel shut off valves, the passenger side one might be partially closed.

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This is a common problem on Pete's and KW's, it's most likely one of the splitter valves. The problem is you can't tell which, because it's an internal issue.

What works the best to solve the problem, if you have shut off valves start closing the return a little at a time to the tank that is more full. Start with a 1/4 turn. Some trucks don't have shut offs on the return, so if you only have them on the draw side close the low tank a little to get the fuel even.

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My T2000 is doing the same thing. Started after I put on a FASS, new fuel lines, 2 new splitters and new tank vents. Pittsburgh Power told me that it had probably always been that way but that the FASS probably made it even more noticeable. They said to just add a 1/4 turn ball valve to one of the return lines going to the fuller tank. Then just start shutting it little by little untill the stay about even. I haven't done it yet so I can't report on how well it works.

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thanks guys! I will look for these valves. Are they usually located right where the lines go into the top of the tank? If so, I don't think I have any valves.

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I'll bet you have either a fuel return line restriction on the right side tank or you have a suction problem on that tank. Either one will cause the fuel to return or draw uneven from the tanks and will then syphon over to equalize the fuel when the engne is shut off.

Either type of restriction will be evident only with the engine running. My guess is that you will find a collapsed line on the suction side or something getting stuck into the fuel line that is removed when the vacuum from the pump ends. Good luck.

I had an experience where I had a vandal place trash and grass into my fuel tanks. With the ehgine running the suction from the pump drew the grass into the fliter head where it choked the line up. After several days of trouble shooting this I drilled a couple of 3/8" holes into the suction line about 1 inch from the bottom. From that point on the trash never got caught on the suction line.

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Thank you jti!!! hopefully I can use that info to get something done finally:-)

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I had same problem on A brandnew 08 t800 and the prolem was they had a pipe plug where the fuel vent was supposed to be It came from the factory like that I put in a vent no more problem

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yeah, I have vent tubes where they are supposed to be, and they are free from obstruction:-)

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I have dual 100 gallon tanks. When the red light comes on near empty I can only put in 120 gallons max. Also after 150 miles of driving a quarter tank will be depleted from the information on the fauge. The Ecm says I'm getting 7 miles to the gallon. The math I do says six. But using both those numbers I cannot match the gauge readings to the mpgs. I already had an overhead done and a new dpf installed. What could it be? Fuel restriction, sending unit, gauge calibration, or bad engine?

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