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Un-even fuel pull from tanks


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I'm seeing un-equal fuel levels in my tanks. The drivers side is the main tank the engine pulls from I think. The fuel level in that tank is 1/4. When I look into the passengers side, it's close to 1/2 tank. It always seems to be about 1/4 'more full' than the drivers side tank.

I have no clue how these tanks are tied together and what part of that would/could obstruct the tank's fuel flow to remain equal.

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Your truck should pull from both tanks and return to both tanks.  The pick up tubes and hoses (both at same lengths) go to a Tee.  So it will draw off the tank with the least resistance, as will the return line will flow to the tank with the least resistance.  By doing this they probably wont be at the exact same level, but somewhat close.  One thing that causes uneven levels would be a dirty or clogged vents.  Which is located at the top of the tank with a hose hanging from it.  One way to verify if they are clogged is to run the truck with the fuel tank cap opened a bit to let it vent from there.  If it levels out it tells you they may be clogged, (best done with less then full tanks) less mess. The vents can be removed and cleaned with a liquid cleaner and reinstalled.  Don't recommend using compressed air to blow them out, it may get the little ball stuck and wont vent, as they say (don't ask me how i know that). 

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I was having a similar problem.  I checked with my dealer.  They said anything growing (microbes) in the fuel line or dirt in the fuel line could cause a restriction on one side or the other.  They recommended running a fuel tank cleaner for the dirt and a biocide for the microbes.  Did both and things now seem better.


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2 hours ago, Nigel said:


You may be worrying about nothing.  I’ve never compared my levels by looking in the tanks.  But when I worked my truck commercially my left tank always took more fuel than the right when filling up maybe as much as 20%.


On my truck the drivers side always shuts off first, but that's the one I always start filling first. Most of the tandem pumps do not give a gallon on each side, but a total only one. There is no way of knowing how many gallons go into each side unless you authorize two pumps or fill one and then turn around and fill the other. I don't worry about it anymore. I used to "Stick" the tanks and at one time thought it would be smart to check for "Water" in the tanks, but never found any place to buy the past I used to use at the "Gas Station" I worked at. Both owners have passed away and nobody I have asked has had any idea what I've asked for. 



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All makes sense.

I filled the drivers side until it read full on the gauge. Drove around and parked for a while. Now the gauge indicates 3/4 full, so some of the fuel migrated to the passengers side tank during the drive.

That would indicate that all is well with that system.

Thanks for the help all.

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