Freightliner Columbia 2006, fuel tanks not equalizing


R

RChesnutt

New Member
Hi,
I am new to driving a truck. Just purchased this Freightliner Columbia, with Mercedes engine, has duel 70 gal tanks. The fuel gauge seems to be reading off the drivers side tank, but when I stopped to fill (gauge read 1/4 tank), my pass side tank was still full. I saw some posts about a clogged vent as a possibility, but when I open the pass side tank cap - should it not then allow it to equalize? or does it use a transfer pump? Any advice appreciated!
 

Check to make sure there aren't shut off valves, some of those had 3-way valves where the the tank lines teed together. Barring that issue, it works like a siphon on the suction side. Returns fuel to both tanks, sucks from the tee. They should equalize with the truck on or off.
 
Nomad1 said:
If it were the tank vents then wouldn't it equalize with the caps off?
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The fuel lines attached at the midpoint on the inside of the fuel tank.


My truck would normally equalize the tanks as it sat there overnight.

But the tanks vent have to be functioning.

Cracking the Caps would do the same thing theoretically
 
mndriver said:
The fuel lines attached at the midpoint on the inside of the fuel tank.


My truck would normally equalize the tanks as it sat there overnight.

But the tanks vent have to be functioning.

Cracking the Caps would do the same thing theoretically
Click to expand...
I thought so. If it were a vent problem I thought you could easily diagnose it by cracking the caps. Then of course you would still have to find the problem.
 
The valves are basic ball valve. Pretty straight forward. Unless a hose is delaminating internally, not likely to be an issue.

We replaced mine and just used common brass ball valves for fuel. They were 1/3 the price of OEM. Got them from the farm supply place at home. Transmission was sitting on the floor so it seemed like a good idea at the time.
 
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Hammer166 said:
Check to make sure there aren't shut off valves, some of those had 3-way valves where the the tank lines teed together. Barring that issue, it works like a siphon on the suction side. Returns fuel to both tanks, sucks from the tee. They should equalize with the truck on or off.
Click to expand...
Tanks don’t hav crossover lines like they used to. They won’t gravity from side to side. Supposed to be equal draw equal return. Vent plugged, Return plugged, or a valve as you said.
 
r3gulator3 said:
Tanks don’t hav crossover lines like they used to. They won’t gravity from side to side. Supposed to be equal draw equal return. Vent plugged, Return plugged, or a valve as you said.
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They will indeed gravity through the suction as long as you have no leaks to break the siphon. A "crossover" can actually be higher than the fuel level once all the air is out of system, so the dip tubes and suction lines function as a crossover.

I've parked on the shoulder with the fuel level low enough that one tank sucked air the next morning after the levels equalized overnight. That was a brain fart on my part that hasn't been repeated! 😉
 
Hammer166 said:
They will indeed gravity through the suction as long as you have no leaks to break the siphon. A "crossover" can actually be higher than the fuel level once all the air is out of system, so the dip tubes and suction lines function as a crossover.

I've parked on the shoulder with the fuel level low enough that one tank sucked air the next morning after the levels equalized overnight. That was a brain fart on my part that hasn't been repeated! 😉
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Your system is not designed to equalize the tanks. That’s antique technology. Equal draw equal return that’s why every fuel line on there is supposed to be cut to a specific length.
 
r3gulator3 said:
Your system is not designed to equalize the tanks. That’s antique technology. Equal draw equal return that’s why every fuel line on there is supposed to be cut to a specific length.
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I understand the dual draw systems, I was merely sharing that they will equalize with the truck off.

And here I'll add that Peterbilt's system is not properly designed, at least on carhaulers. Everyone I know has to fiddle with the shutoff valves to keep fuel levels equal. Only issue on Western Stars is very strong crosswinds at low fuel levels. The different pressures on the vents will cause a dry tank sooner than normal. I've thought about teeing them together to make sure both vents a seeing the same pressure.
 
Hammer166 said:
I understand the dual draw systems, I was merely sharing that they will equalize with the truck off.

And here I'll add that Peterbilt's system is not properly designed, at least on carhaulers. Everyone I know has to fiddle with the shutoff valves to keep fuel levels equal. Only issue on Western Stars is very strong crosswinds at low fuel levels. The different pressures on the vents will cause a dry tank sooner than normal. I've thought about teeing them together to make sure both vents a seeing the same pressure.
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That’s interesting. My tanks don’t have shut offs, one tank is 25 gallons smaller than the other but they empty equally. 🤷🏻‍♂️
 
I had a 2006 Volvo w/Cummins ISX starve out and coast into a rest area. One tank was bone dry and the other overflowed when I took the cap off.

Temperature was below zero.

After it sat a few minutes it would idle but it would starve out if I tried to drive it.

I limped it to the next truck stop and filled the empty tank and then it ran fine.

My delivery was the next morning, 60 miles past my company's HQ so I stopped in there and that tank was low again and the other was still overflowing when I tried to remove the cap.

So I unhooked the trailer, put the bobtail in the heated shop and found an unassigned Peterbilt with nobody's stuff in it, parked in the lean-to and plugged in. I "stole" it to deliver the load in Sioux City and by the time I got back they'd already put the Volvo outside. Mechanic told me the fuel had equalized by morning and the vents were clear but he drained "about a cup" of water out of the tanks.

I had no further issues with that truck.
 
I know if I fill one tank only, it will seek it's only level and both tanks will be level with each other.

That's either by letting it sit overnight on its own or by driving it and it balances on its own.

With the sending unit on the driver's side, it will drop quickly to a level depending on how much fuel I had when it was filled. You could pretty well split the before and full marks and that's where it settled tom
 
Duck said:
I had a 2006 Volvo w/Cummins ISX starve out and coast into a rest area. One tank was bone dry and the other overflowed when I took the cap off.

Temperature was below zero.

After it sat a few minutes it would idle but it would starve out if I tried to drive it.

I limped it to the next truck stop and filled the empty tank and then it ran fine.

My delivery was the next morning, 60 miles past my company's HQ so I stopped in there and that tank was low again and the other was still overflowing when I tried to remove the cap.

So I unhooked the trailer, put the bobtail in the heated shop and found an unassigned Peterbilt with nobody's stuff in it, parked in the lean-to and plugged in. I "stole" it to deliver the load in Sioux City and by the time I got back they'd already put the Volvo outside. Mechanic told me the fuel had equalized by morning and the vents were clear but he drained "about a cup" of water out of the tanks.

I had no further issues with that truck.
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Sooooo.... what I took away from this story is, you had to use a Peterbilt to finish a job that a Volvo couldn’t. 🤣
 
I had a 13 letter shit spreader back in 2005 that would drain the drivers side tank and the passengers side tank would be near full.
I must have gone to 4 different shops including the company shop. They never did find the problem before they traded it in.

You are welcome, Glad I could help! :thumbsup:
 

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