duel fuel tank question

[naive]

I have a real entry level question... I just got this 1968 c 30 Open Road camper. I'm going to go fill it up for the first time.
It has two fuel tanks and I am wondering how the fuel gauge works? I have a switch next to the drivers seat that says "gage"... I guess if I switch it it'll show the level in the other tank?
Does this also open up the second tank when the first is empty or are both tanks linked and they drain together?

Thanks

[kwmech]

Another pic of the gauge switch? Most of the early trucks did not have a gauge attached to the different tanks. You just ran the tank down until the engine started to sputter and turned the valve on the floor and waited until the engine caught itself again. My 68 has dual side (travel) tanks with a 3 way valve on the floor, gauge only works on the seat tank. My guess is with what you are showing in the picture is when the valve is in that position is when you are on the seat tank. Any other placement of the valve and you on your own to guessing to when you will run out.

[truckster]

You'll have to manually switch the tanks and the gauge separately. The valve in your picture switches the tank lines; the switch on your dash switches the gauges.

[71threequarterton]

That looks like the valve I have on the floor in my truck but mine is a three position valve. I have the standard primary tank behind the seat and then the saddle tanks on the sides under the bed. My gauge only works with the primary tank. I can only run off one tank at a time and switching between the tanks is done manually by twisting that valve to the desired position. It does not happen automatically.

[72chevynut]

It must have been a separate option to have a switch on dash to read each tank fuel level. One of my K20's has the three fuel tanks with the tank selector valve down beside seat on floor. Then on the dash it has a toggle switch to read fuel level in each tank using same fuel gauge in instrument cluster.

[naive]

Thanks everyone for the responses, your knowledge is great!!
I wish this lever was marked with positions.

Here is a weird update... When I left, the fuel gauge needle was showing 1/8th of a tank, didn't change whatever the position of the floor switch... I put 12 gallons into the drivers side tank, still no gauge change even after moving the floor switch. So I guess the gauge is broke. The needle did rise when I drove down a hill :-)

Originally Posted by truckster

You'll have to manually switch the tanks and the gauge separately. The valve in your picture switches the tank lines; the switch on your dash switches the gauges.

I don't think I have a dash switch to control the fuel gauge, unless I'm just missing it somehow??? Could it be under the dash somewhere?
I'll attack some pics.

Also, can someone identify these hard tubes on either side of the cab? gas tank vent?

Way more questions than answers with this old truck.

Thanks everybody

[Stocker]

Originally Posted by 72chevynut

It must have been a separate option to have a switch on dash to read each tank fuel level. One of my K20's has the three fuel tanks with the tank selector valve down beside seat on floor. Then on the dash it has a toggle switch to read fuel level in each tank using same fuel gauge in instrument cluster.

That's exactly the same as my K20.....

No idea what those tubes on the sides of the cab are for. Can you trace them down to see where they come from?

[naive]

Originally Posted by Stocker

That's exactly the same as my K20.....

No idea what those tubes on the sides of the cab are for. Can you trace them down to see where they come from?

Thanks Stocker
I'll definitely crawl under there tomorrow and investigate.