adding a second gas tank

[Troy35]

I've searched, and while there are a lot of gas tank topics on here I couldn't find my answers. I would very much like to put a gas tank under my driver seat and plumb it into my rear mounted factory tank to give me 30 gallons of gas. Cargo space is of course at a premium in the CJ5 and I'd prefer to not carry Jerry cans with me. 30 gallons of gas would get me anywhere I wanted to go without fear of worrying if I'll make it to the next gas station. So I was wondering:

1. I know I need a "vintage" tank; like 55-72 I think. Can someone tell me the best/least expensive place to get a tank? I'd prefer new just to avoid dirt, junk, debris. Is there a best tank for this application?

2. Also, with the new tank I will need to made a fill neck on the side of the jeep behind the driver seat. Again, where should I go for that part and the trim piece?

3. I would like to plumb the two tanks together. I have an idea how I would like to do it, but is there a kit out there? If I just plumb to the lower part of the higher sitting unseat tank to the top of the lower sitting rear mount tank would that work?

Thanks!

 

[Hedgehog]

If you plumbed them together directly you'd run into trouble with the overflow valve. If you did away with the lower overflow system, you might end up with excessive hydrolic pressure. I've thought about doing the same thing you are doing. I believe you'd have to install a switch designed to switch tanks. It would be cool to have a device that would allow gas to flow from one tank to the other when the fuel level got low enough in the bottom tank to allow it to take the entire volume of the upper tank. You coule do it manually, but if I were doing this I absolutely know that I'd forget to switch and would over flow the bottom tank.

 

[dagr8tim]

If you plumbed them together directly you'd run into trouble with the overflow valve. If you did away with the lower overflow system, you might end up with excessive hydrolic pressure. I've thought about doing the same thing you are doing. I believe you'd have to install a switch designed to switch tanks. It would be cool to have a device that would allow gas to flow from one tank to the other when the fuel level got low enough in the bottom tank to allow it to take the entire volume of the upper tank. You coule do it manually, but if I were doing this I absolutely know that I'd forget to switch and would over flow the bottom tank.

Why not use like a ball valve. When you get low, open the valve and purge the upper tank into the lower tank. Then you could fill the tanks separately, and just open the dump when you needed/wanted too.

 

[johnnyreb]

ive been rolling this idea around in my head for years. I was gonna use adual tank switch valve. yours will probally be easier than mine as after 76 the changed the floors.
Many of the supply places sell the tank, the grommet and the sheet metal insert. Look at kaiser willys or willys-overland.

 

[Hedgehog]

Why not use like a ball valve. When you get low, open the valve and purge the upper tank into the lower tank. Then you could fill the tanks separately, and just open the dump when you needed/wanted too.

Because there would be too much oppertunity to forget to close the valve. I know I'd forget and make a mess, let alone the danger involved, when filling up.

 

[Kilo19]

i read up on this a while ago, and the best thing i saw was chevy makes a good fuel pump switch. correct me if this is wrong, but this is how i understood it to be laid out

dual fuel pump, connected to one fuel line in the cab with a manual or electric switch for seat tank or back tank, and have power run to each, set up the gauges to both, with the electric switch, so which ever tank is "switched on, the gauge reflects that"

Thats how im doing mine.

 

[tarry99]

I've searched, and while there are a lot of gas tank topics on here I couldn't find my answers. I would very much like to put a gas tank under my driver seat and plumb it into my rear mounted factory tank to give me 30 gallons of gas. Cargo space is of course at a premium in the CJ5 and I'd prefer to not carry Jerry cans with me. 30 gallons of gas would get me anywhere I wanted to go without fear of worrying if I'll make it to the next gas station. So I was wondering:

1. I know I need a "vintage" tank; like 55-72 I think. Can someone tell me the best/least expensive place to get a tank? I'd prefer new just to avoid dirt, junk, debris. Is there a best tank for this application?

2. Also, with the new tank I will need to made a fill neck on the side of the jeep behind the driver seat. Again, where should I go for that part and the trim piece?

3. I would like to plumb the two tanks together. I have an idea how I would like to do it, but is there a kit out there? If I just plumb to the lower part of the higher sitting unseat tank to the top of the lower sitting rear mount tank would that work?

Thanks!

On your first question the internet is full of stock replacement under seat tanks both steel and plastic composite with the correct neck that will extend out the side of your body.

The trim piece you refer to is normally just a rubber grommet that the neck passes through , since you now I believe have a block off panel in that location a hole just needs to be cut. If your Jeep is not equipped several suppliers sell that panel for earlier versions CJ's

As far as your last question there are numerous on line solutions for dual tanks that use an electrical or manual valve that in some case's allow switching , blending and a gauge to monitor both.

Keep in mind that in your 75 CJ you have a closed system for venting, most below the seat tanks are not set up that way and are vented at the cap only. In order for the fuel pump up front to equally draw fuel they also need to be close to the same elevation. The room between the top of the fuel tank and the seat is close so venting there could be an issue.

Not to say all this cannot be accomplished but the variables are many.

Some Jeep owners as I , have eliminated the inside fuel tank for several reasons......one being the fuel smell inherent with the tank being in there and the related safety issue. A 15-20 gallon tank in the rear seems to be adequate at least for me and when we do go in the woods we always carry extra fuel in Jeep cans that are left at camp.

 

[Troy35]

Ok, well it sound like this may be more of an engineering project than I thought. I may hold off on the idea for a little while and continue my research. Thank you. I'll post updates when I decide how to best plumb my setup when I do it.

 

[Torxhead]

I put an additional saddle tank that was purchased at a junkyard in my Chevy pickup a few years back and it went quite well. I used that GM fuel pump switch that I bought from a local auto parts, connected it to the fuel level senders, and gas gauge, plumbed it and used a toggle switch. They were both vented thru the charcoal cannister. So the switch opened one tank and the fuel gauge read that tank, it held 40 gallons. Personally in the Jeep, I would rather use one rear tank and carry jerry cans as needed.

 

[CJDawg]

Thought I would show you the switch for the 2 fuel tanks on my CJ6 . One switch changes tank and other changes gauge. That's all I know about it.

 

[IOPort51]

the elevation would only be a problem if they filled from the same neck. The switching valve would decide which tank the fuel was sucked out of not drained out of.

Did the early scout have twin tanks? I seem to remember a tank in the wheel well ?

 

[TroyaCantrell]

Thought I would show you the switch for the 2 fuel tanks on my CJ6 . One switch changes tank and other changes gauge. That's all I know about it.

Did you have them installed or did it come that way to you? Can you tell me anything about the second tank. Location, fill neck location? Got a 6 myself and the little under seat tank is so small.


Troy Cantrell
Sent from my iPhone using Tapatalk
Build thread - '66 CJ6 :
http://www.jeep-cj.com/forums/showthread.php?t=15075

 

[cjk5]

Could you let me know how it goes if you do it. The idea sounds amazing and if it works out good I might do it myself.

 

[NorthwestCJer]

I added a tank under the rear of a 67 CJ5 many years ago. The 67 originally had a under seat tank. I took a tank out of a DJ5 postal and bolted it under the CJ. I used a three way ball valve and mounted it between the drivers and pass seat on the floor. The lines were under the jeep and the handle on top.
I had no issues with it.
Since yours does have a different vent system. Just get a vented fuel cap for the rear tank. If you have a fuel return line on you intermediate, use from the back tank first. So if fuel does return threw the system, it will return to a empty tank and not a full one.
I would recommend adding the secondary tank under the pass side, and not the drivers. I hated the leg room the tank takes up under the drivers side. You would have to remove the under seat storage box, but those are usually huge rust traps anyway.

Good Luck

 

[TroyaCantrell]

That's good stuff, thanks !


Troy Cantrell
Sent from my iPhone using Tapatalk
Build thread - '66 CJ6 :
http://www.jeep-cj.com/forums/showthread.php?t=15075

 

[tarry99]

I added a tank under the rear of a 67 CJ5 many years ago. The 67 originally had a under seat tank. I took a tank out of a DJ5 postal and bolted it under the CJ. I used a three way ball valve and mounted it between the drivers and pass seat on the floor. The lines were under the jeep and the handle on top.
I had no issues with it.
Since yours does have a different vent system. Just get a vented fuel cap for the rear tank. If you have a fuel return line on you intermediate, use from the back tank first. So if fuel does return threw the system, it will return to a empty tank and not a full one.
I would recommend adding the secondary tank under the pass side, and not the drivers. I hated the leg room the tank takes up under the drivers side. You would have to remove the under seat storage box, but those are usually huge rust traps anyway.

Good Luck

I would agree on the leg room under the drivers side being tight but I would never give up my Passengers side tool box..........way to handy to store things in......in fact I'm pulling my drivers side under seat tank out now and building another tool box for the drivers side out of aluminum......then I'm building a new aluminum tank for the rear......I think I can get about 18 gallons there without sacrificing ground clearance........The 18 will give me pretty good range and if the trip requires I can still carry two 5 gallon cans.