How do I use the tank selector on 1973 Camper Special

[Arroyo083]

Hi there! Just bought this 1973 Camper Special. I have a manual selector on the floor area, closest to the driver’s side door. I’ve never owned one of these trucks and today the long part of the valve was completely straight up, pointing towards the sky. Don’t believe my gauge/sending unit is working right because it shows past full. So, I stopped and filled one 20gal tank, the driver’s side. Drove about 100 miles, went to fuel up to be safe and to see how much she drank. I got 1 gallon in it before it started overflowing. So, I put gas in the right one, adding 10 gallons. How does the dual tank system work? Does only one tank work and previous owner didn’t tell me? Did I fill up a 20 gal and now need to pump it out? Do I switch the valve to the other side and drive? Valve seems to only point strait up, meaning with the long part of the valve/handle or to the driver’s side. I can barley move the long part/handle toward the passenger’s side/door. Idk what I’m doing haha. Please Help! Thank you!

 

[78C10BigTen]

This sounds like we need pictures for clarification... im a little confused here.

 

[75gmck25]

That is an aftermarket dual tank system, probably dealer installed, so it’s difficult to know exactly how it works.

The original GM system uses a dash mounted DPDT rocker switch and a 3 or 6 port fuel solenoid under the truck. In ‘73, with no switch power (“right” position) the solenoid defaults to the main/right side tank. When you move the dash switch to the “left” position it powers the solenoid and switches to that tank. Six port solenoids are used if you have a return line on the fuel pump because you need to switch both supply and return. The original dash switch is DPDT because it also switches the fuel gauge wiring from one tank to the other.

On a ‘73 the main tank is the passenger side, so a single tank truck would only have a tank on that side. If the switching solenoid for the dealer-added dual tank system is not working, the truck probably just stays on the main/right tank all the time.

FYI - GM changed the setup in later years and the left side became the main tank. They also changed to a fuel solenoid with six electrical terminals, instead of the early version that just has a single power terminal.

 

[Arroyo083]

Here are all photos I took! Thanks for the reply! It’s like 1st owner deleted that (your right) drivers side option. Idk if R means right or reserve.

 

[RetroC10Sport]

Similar to the setup on Big Bertha. Hers doesn't work either so the owner is switching to a factory setup when she can.

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[Arroyo083]

Hmmm. Idk if it works or not lol. Guess I gotta keep driving her until I find out the hard way.

 

[Grit dog]

I’m gonna guess R means right. Never heard of a reserve on any vehicle.
The valve is probably a 90 deg turn from one to the other tank but it’s aftermarket so idk.
On another note…How big is that aftermarket tank?
Must be bigger than OE 20 gal tanks or why would anyone have gone through the trouble since the OE tanks are interchangeable and always have been.

 

[Arroyo083]

All great questions. Older man I bought it from didn’t know much. He bought it from his friend who owned it since he bought it new. Had the camper when he bought it but sold it to a different friend. Old man I bought it from bought it from first owner in 2018 and said he didn’t drive it so he got rid of it. I’m the third owner supposedly. Runs like a dream.

 

[78C10BigTen]

All great questions. Older man I bought it from didn’t know much. He bought it from his friend who owned it since he bought it new. Had the camper when he bought it but sold it to a different friend. Old man I bought it from bought it from first owner in 2018 and said he didn’t drive it so he got rid of it. I’m the third owner supposedly. Runs like a dream.

Gorgeous truck! My favorite nose too!

 

[Grit dog]

More great questions? The underside of the seat tub there looks unnaturally clean and shiny. And I’ve never seen a pink/red underside paint, unless was the truck originally red and repainted the current color.
Another question. 73 wouldn’t have had return line from the fuel pump originally. But that’s a 6 port valve so must have a return line?

That valve handle, has a knurled nut on the bottom. Is that a lock to prevent inadvertent switching? Or does it just hold the handle on? Have you loosened it?
Valve could just be stuck. Obviously it’s running off of the right side tank based on your post, even though it’s not pointing at “R”.

 

[bucket]

More great questions? The underside of the seat tub there looks unnaturally clean and shiny. And I’ve never seen a pink/red underside paint, unless was the truck originally red and repainted the current color.
Another question. 73 wouldn’t have had return line from the fuel pump originally. But that’s a 6 port valve so must have a return line?

That valve handle, has a knurled nut on the bottom. Is that a lock to prevent inadvertent switching? Or does it just hold the handle on? Have you loosened it?
Valve could just be stuck. Obviously it’s running off of the right side tank based on your post, even though it’s not pointing at “R”.

That red oxide color was the type of sealer they used in the 70's on trucks, K5's and Suburbans too.

 

[Grit dog]

That red oxide color was the type of sealer they used in the 70's on trucks, K5's and Suburbans too.

Wow, then that is in really good shape!

 

[75gmck25]

I don’t know when GM started using fuel pumps with a return line, but my ‘75 K25 with HD emissions (8400 GVW, no cats) has a factory steel fuel return line and non-vented gas caps with a steel vapor line running to the vapor canister under the hood. The original Quadrajet part number of my carb is listed for California emissions, so maybe that was the setup.

From the factory my truck only had the passenger side tank, so I cobbled together the dual tank setup using parts from junkyard trucks. I was lucky and found one with the old six port solenoid that has only one power terminal, and it continues to switch properly. However, the new 3 port sending units from Autozone are a little off at the low end, and it seems to have at least 4 gallons left when the needle touches empty.

 

[WebMonkey]

looks like a push/pull stem rather than a twist left/right.

good luck!

 

[mcarlo86]

That auxiliary fuel tank looks like something added by a camper dealer. It was pretty common to add them to pickups when slide in campers were purchased to add more range. The ones I have seen set up that way did not have the fuel gauge hooked up, so the gauge only worked for the factory passenger side tank. Similar to when saddle tanks were added to old C50/60 grain trucks that had a factory cab tank behind the seat. Guys would run off the bigger aftermarket tank until they ran out and then would switch to the smaller factory tank as the "reserve". The valve may be hard to turn due to corrosion/rust. I would imagine either a 90 degree or 180 degree turn would switch it back to the factory tank. Might want to drain that factory tank if it hasn't been used in a long time. Who knows how old that gas might be! What does the driver's side fuel fill look like? '73 would have had the passenger side tank as the standard tank and the drivers side would have been optional I believe.