Dual fuel tank ideas 77 wagoneer

[Sdsurfer]

So I’m starting the process to replace the rear leaf springs and replace some electrical wires and re-run brake lines so mine as well drop fuel tank and replace fuel lines….

Before I get to far down the fuel line path I wanted to see what others have done or thought about 2 fuel tanks. previous owner installed a second tank in rear underside where spare tire went and installed an Eletrical switch that you can select which tank goes to mechanical fuel pump. Looks like at fill neck the line splits and you fill both tanks. Does not appear that the return line is still installed but still appears to have main tank vent.

I’ve heard stock tank is problematic…? Thoughts on best way to approach? I like the idea of 2 tanks for extra fuel capacity but I’m not sure how much I would need it as I don’t plan long distance off-roading anytime soon.

[sierrablue]

I'm pretty sure mine had pretty much the exact same setup yours does, at some point. No spare tire anywhere to be found, and some weird lines stuffed between the tank and the frame.

Some people claim the factory tanks are super wimpy, and as soon as you scrape them they'll have a puncture, which probably has some truth to it if you're rock crawling. The replacement plastic ones are supposedly a nightmare to install, and they have like a 1-2 gallon smaller capacity.

Personally I think you should pick one and stick with it, unless you're spending lots of time driving it away from gas stations. The stock 24 gallon (or whatever it is) tank is plenty even for lower 10s mpg. At 10 mpg you should be able to go 230 miles for sure with some left over in these. It's easier, fewer potential leaks and problems, less weight, and the DOT is going to be much happier with the stock one (the DOT absolutely HATES tanks behind the rear axle, more so on unibody cars, but on anything).

It might be cool to plug the vent on the stock tank, and set up the new tank to refill the front one through the filler hose, with the vent on the extra tank...that would probably be super complicated though.

[tgreese]

Was looking at the Aerotanks site a couple of days ago. They list a replacement tank that replaces the factory tank and holds 40 gallons. https://aerotanks.com/product/1974-1979 ... ment-tank/

According to the page, you can keep your factory spare location. Presumably you could have this tank plus a behind-the-ale tank, giving you another 20-ish gallons capacity.

Prior to 1980, the skid plate for these optional. My '77 J10 came with (and still has) no skid plate. Certainly the bare steel tank would not resist rock puncture very well. Perhaps this is where the claims above come from, though I have not personally heard such claims. The factory skid plate should be fine, both for the steel tanks and the later plastic tanks (if not rusted away).

My J20 came to me with an aux tank behind the axle. It has a separate fill, that was not complicated to install. Using the same fill for both tanks seems a bit sketchy to me - not a problem to install a second filler neck and cap, AFAIK.

The electric valve/switch is available in a 6-way version that switches both the feed and return. It also handles switching the gauge between the two tanks. in '77 a 49-states V8 may have vapor recovery - I'd have to look at the book. A CA car definitely will. My '77 258 does not. Not valve needed for that - just tee in the vapor line from the new tank to the vapor line from the factory tank going forward.

[sierrablue]

Interesting that Aerotanks claims '74-'79 when the '70-'77 all have identical tanks (except maybe for some emissions fittings), and '78-'79 has a different (better) filler neck assembly. I also question how far that tank hangs below the frame.

I don't recommend a skid plate if you plan to drive it in the winter on the street. It collects salt and snow and water, and before you know it, the frame is rusting out (the reason we got rid of the '88)

[tgreese]

You don't have any option on an '80 or newer Wagoneer. The tanks for those years are plastic and must be supported by the skid plate. Thus the skid plate is not optional for those years.

The skid for earlier steel tanks hangs by brackets, and is not in contact with the tank. AFAIK rust is not a problem for those - the open design allows debris to exit. The later design traps debris and rusts, but it must be there.

[Sdsurfer]

Thanks for the info all.

That’s good to know on skid plate. So for my 77, I can remove skid plate and the tank won’t drop? It would make it easier to get to front leaf spring bolt if skid plate is off.

I’ll probably take off the secondary tank and try running just the original tank and see how that goes. Makes stuff simpler.

Do you all recommend using the return line? Right now I got a manual fuel pump and probably will keep that for a while due to simplicity but if I run electric the return line would be nice.

Also do I need the breather on the original tank…?

[SJTD]

They want 650 bones for a tank and they don't even have actual pics?

[tgreese]

... I can remove skid plate and the tank won’t drop? ...

If you look under the Jeep, it should be obvious. The factory steel tank bolts to the body. There should be space between the tank and the skid, or some kind of spongy pad. The spongy pad is often gone, because it traps water and makes the bottom of the tank rust and leak. Not needed.

... Do you all recommend using the return line?...

Up to you. Plenty of discussion in old posts, if you search. Likely in other forums too.

...Also do I need the breather on the original tank…?

You need a vent, whether that's a vented cap or the vapor recovery system (charcoal canister, FTVC in the TSM). Not usually called a breather.

[sierrablue]

Thanks for the info all.

That’s good to know on skid plate. So for my 77, I can remove skid plate and the tank won’t drop? It would make it easier to get to front leaf spring bolt if skid plate is off.

I’ll probably take off the secondary tank and try running just the original tank and see how that goes. Makes stuff simpler.

Do you all recommend using the return line? Right now I got a manual fuel pump and probably will keep that for a while due to simplicity but if I run electric the return line would be nice.

Also do I need the breather on the original tank…?

Yeah, removing the skid plate should be fine; as tgreese said, the tank bolts to the frame.

On the early ones, the rust on the frame may not be as big of an issue, but the way they're designed I think it is.

I do recommend the return line. If you take it out/plug it, then your odds of vapor lock go up dramatically. Even down here at 700 feet, when it's hot, I've had issues when the return line was plugged off. With it not plugged off, I've only had issues when it was 90°+, and I went from cruising at 60 mph to a stoplight at 0. And my fuel line has a bad habit of always ending up right against the power steering bracket on the head, so it gets warmer than it should (I should just bend a new one now that we have some line...). It's not going to hurt anything and can definitely help.

[tgreese]

They want 650 bones for a tank and they don't even have actual pics?

Maybe they have not built one since web sites became a thing. They have a picture of their behind-the-axle tank. Worth a phone call or email if someone were interested.

[devildog80]

Some day would like to do this on my '84 GW, as my primary planned use is pulling a camper, and mostly road trips.

Would set up with separate fill, and dash switch for tank and gauge function.

Spare tire will go inside, up on top, front/rear bumper, as long as it's onboard I am good.