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MJ LB Dual 24gal Tanks?


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I was looking into relocating the gas tank on the passenger side. I am going to run the exhaust straight back. I will be able to do that, as I am going with a Dana 300 (not flipped). Dana 44 PS drop.  I was thinking of welding the hanger brackets to the other side of the frame. The thought of keeping the gas tank where it is has also crossed my mind. Of course, where do you put the muffler? So, I was thinking of a SuperTrap muffler. Just ramblings. Also, would need a heat shield between the exhaust pipe and the gas tank.

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I have looked at adding a 2nd gas tank to the Comanche for 10 years.  Finally decided it was not worth the work.

 

One member here has installed a stock 18 gallon tank on the passenger side to supplement the stock 23.5 gallon fuel tank.  So it can be done.

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2 hours ago, johnj92131 said:

One member here has installed a stock 18 gallon tank on the passenger side to supplement the stock 23.5 gallon fuel tank.  So it can be done.

 

I considered this on my LWB.  Either use a factory tank on the passenger side, or something else, but it has to be smaller than the other one and set farther back, so you can turn the exhaust up and over the frame before it...  I don't see there being room for satisfactory routing of the exhaust between, above, or below two tanks.

 

I also have an odd year YJ tank (it's plastic, apparently it's sorta rare) that I was going to try using where the spare would normally go.

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You guys ROCK! :D Great suggestions and comments. 

 

Exhaust would be easy enough to customize.

 

Options:

1) Turn it (shorten) out in front of the right rear wheel.

2)  Turn it (shorten) out behind the right front wheel.

3) Go into the rail. This sounds bonkers, but it's just a 1 3/4" or 2" exhaust pipe.

 

Those are just some ideas for now until I do it.. and I'm gonna. Cost would be anywhere from $100 (used junk yard price) to $400 all new OEM I'sd suppose. 

 

Why not, right? I've driven trucks w/dual tanks and LOVE it. I may 'bob' the Long Bed, so I'll have to keep all major components in front of the rear axle. 

 

I use to rebuild totaled (those that look like crumpled tin cans) automobiles, trucks, vans, etc.. so no worries w/the exhaist mods. Just curious how I'd rig it to switch while driving. I suppose I'll research some F250's w/dual tanks to see.

 

Anyone local to Birmingham Alabama have a used 23.5-24 gallon MJ fuel tank or know where I can find one?

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12 hours ago, MJsNotDead said:

Exhaust would be easy enough to customize.

 

 

Options:

1) Turn it (shorten) out in front of the right rear wheel.

2)  Turn it (shorten) out behind the right front wheel.

3) Go into the rail. This sounds bonkers, but it's just a 1 3/4" or 2" exhaust pipe.

 

You have actually looked at how the tank sits in there relative to the cab?  There isn't space to get it between the tank(s) and the cab, unless as I said you use a smaller tank and go over the frame rail in front of the tank (and dump in front of the tire, or whatever).  So you can't accomplish #1 without hacking it through the frame, or not easily at least, which I think is what you mean with #3.

 

#2 is a terrible idea.  You will be choking on fumes.  It is bad enough dumping it in front of the rear tires for anything that sees slow speed usage.  If you're going to do #2, you'd be better off running a hater pipe through the hood and just owning it.  At least it would be high school cool.

 

Hacking a hole through the frame (under the cab) to get it through it would work for #1, but has a couple major considerations.  Not matter how you do it you will significantly reduce the cross sectional strength of the frame, regardless if you plate it or sleeve it, as the hole needs to be larger than the pipe to account for an air gap (2.5" ID minimum, since running anything smaller than 2" exhaust is really choking the engine) or you will have significant heat transfer to the frame rail which will weaken it and make it extremely susceptible to corrosion attack.  I'm not home and don't have a MJ here, but IIRC the frame is only 3.75" or so tall in that area towards the back of the cab, if you cut out 2.5" of that it's just more than what is comfortable.  You could do an oblong hole and run a similar shaped pipe through it though, and maybe that would be the solution, but it is the type of mod that there's no going back from.

 

Heat management is a big thing too.  The factory ran the exhaust in a fairly complicated manner for this reason,  you need a significant air gap/flow and/or heat shielding between the exhaust and fuel lines/tanks as you can cause the fuel in a tank or the lines to boil fairly easily.  This all becomes worse if you're going to throw skidplates on things, as it really cuts down on the airflow and traps the heat in places it wouldn't be otherwise.

 

If by #3 you mean running the pipe inside the frame down the length of it, I really suggest you don't.  Heat and corrosion issues are the big thing, plus it would actually be a nightmare to bend it up to fit that.

 

I guess it comes down to how much more fuel you're looking to get in there, and how far you're willing to go with hacking things up.

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On 6/14/2018 at 4:30 PM, DirtyComanche said:

 

I considered this on my LWB.  Either use a factory tank on the passenger side, or something else, but it has to be smaller than the other one and set farther back, so you can turn the exhaust up and over the frame before it...  I don't see there being room for satisfactory routing of the exhaust between, above, or below two tanks.

 

This is the best idea I have seen yet for this problem.  I'm looking to do this on my lwb tdi conversion project and had always thought I would find a way to route it over the driveshaft, but even if that is possible it would still require that space at the front for the exhaust to go up, going over the gap between the frame and bed seems a lot easier.

 

Stock 18 gal swb tanks are about 6in shorter than lwb 23 gal tanks, think that's enough of an air gap to prevent excessive vaporization of gasoline?  If I end up doing this it will be with diesel so I'll have a little extra leeway as diesel doesn't really like to vaporize but it would still be nice to know about the gasoline.

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Why do you want dual tanks on a Comanche with a TDI engine conversion?   10 years ago, I thought it would just be a cool idea. Here is a link to an old discussion:  https://comancheclub.com/topic/12482-second-gas-tank-in-an-mj/

 

The TDI engine gives you a good 30 mpg and the 23.5 gallon tank gives you a very comfortable 600 mile range before you need to think about refilling with diesel.  My bladder will require a pit stop long before 600 miles.  With my 96 Passat TDI, I have actually done 1200+ miles on a single tank with personal pit stops along the way.

 

The TDI conversion works very well on the Comanche!  Here is a link:  https://comancheclub.com/topic/52550-86-diesel-mj-to-vw-tdi-conversion/

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16 hours ago, DirtyComanche said:

 

You have actually looked at how the tank sits in there relative to the cab?  There isn't space to get it between the tank(s) and the cab, unless as I said you use a smaller tank and go over the frame rail in front of the tank (and dump in front of the tire, or whatever).  So you can't accomplish #1 without hacking it through the frame, or not easily at least, which I think is what you mean with #3.

 

#2 is a terrible idea.  You will be choking on fumes.  It is bad enough dumping it in front of the rear tires for anything that sees slow speed usage.  If you're going to do #2, you'd be better off running a hater pipe through the hood and just owning it.  At least it would be high school cool.

 

Hacking a hole through the frame (under the cab) to get it through it would work for #1, but has a couple major considerations.  Not matter how you do it you will significantly reduce the cross sectional strength of the frame, regardless if you plate it or sleeve it, as the hole needs to be larger than the pipe to account for an air gap (2.5" ID minimum, since running anything smaller than 2" exhaust is really choking the engine) or you will have significant heat transfer to the frame rail which will weaken it and make it extremely susceptible to corrosion attack.  I'm not home and don't have a MJ here, but IIRC the frame is only 3.75" or so tall in that area towards the back of the cab, if you cut out 2.5" of that it's just more than what is comfortable.  You could do an oblong hole and run a similar shaped pipe through it though, and maybe that would be the solution, but it is the type of mod that there's no going back from.

 

Heat management is a big thing too.  The factory ran the exhaust in a fairly complicated manner for this reason,  you need a significant air gap/flow and/or heat shielding between the exhaust and fuel lines/tanks as you can cause the fuel in a tank or the lines to boil fairly easily.  This all becomes worse if you're going to throw skidplates on things, as it really cuts down on the airflow and traps the heat in places it wouldn't be otherwise.

 

If by #3 you mean running the pipe inside the frame down the length of it, I really suggest you don't.  Heat and corrosion issues are the big thing, plus it would actually be a nightmare to bend it up to fit that.

 

I guess it comes down to how much more fuel you're looking to get in there, and how far you're willing to go with hacking things up.

People who can, do.  People who do, don't ask how. 

 

 

I used to argue with people, then I realize that everyone has to learn on their own. 

 

 

There are also a couple of reinforcement plates within the frame rail (I ran wire through the frame), no one is going to run exhaust through the frame. 

 

Fuel tank at the rear, tank from a Chevelle or Impala or other 70s car hung from the rear x frame section with the filler door in the floor of the bed..........something like that would be easiest to fab........and most practical. But then you lose spare tire.........have to fab a proper door........etc..........

 

 

Suggest to someone here that they buy a proper transfer tank that bolts in under a tool box at $1000+++ ............watch their eyeballs bleed. Everyone want's something for nothing. 

 

 

Then, there is this-

https://www.overtons.com/modperl/product/details.cgi?pdesc=Scepter-Portable-12-Gallon-Fuel-Tank&i=321079&CAWELAID=120030620000069287&s_kwcid=adwords__&gclid=Cj0KCQjw6pLZBRCxARIsALaaY9ajdByrc2NmpMlKA1aNZo0ry45zJvR-drEq-EYeiq2-RnoUumNyQuAaAtMTEALw_wcB

 

Two will slide under a tool box, plumbing is another matter but that is easy. 

 

 

 

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9 hours ago, Jeep Driver said:

Fuel tank at the rear, tank from a Chevelle or Impala or other 70s car hung from the rear x frame section with the filler door in the floor of the bed..........something like that would be easiest to fab........and most practical. But then you lose spare tire.........have to fab a proper door........etc..........

 

That's why I said a YJ tank, it's kinda the right shape to fit behind/in the crossmember nook where the spare normally lives.  I saved a fuel filler panel/door/neck out of an XJ I cut up and planned to hack into the inside of the bed to make it all work.  That said, I don't know if it would have worked, there was potential for needing to cut up a bunch of stuff including parts of the frame that are rather structural.  Which could be done, but may not have been a good idea. 

 

The 90s S10 Blazers had a tank that also would likely fit.  For muscle car tanks there was one that I thought had a good chance of fitting, I want to say it was a Camaro, but with no hope of finding one in a junkyard I didn't pursue it.

 

I have the YJ tank, just never got around to trying to fit it.

 

Cheapest option is an old drum and a siphon hose...  205L, roughly 3 times the capacity of the stock SWB tank. :roflmao:

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23 hours ago, johnj92131 said:

Why do you want dual tanks on a Comanche with a TDI engine conversion? 

I agree the diesel conversion will take care of any range issues.

 

Part of the project is to have the bed able to convert to a mini camper that can be used year round possibly even on a ski trip; so I have a diesel powered hydronic coolant heater, usually designed for preheating engines, but are used by many people building expedition vehicles to provide heat and even hot water with the engine off.  The second tank would mostly be to run that for as long as I want without eating into vehicle range.

 

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2 hours ago, johnj92131 said:

Ford F-150 rear 19 gallon tank will fit in place of spare tire. Mid 90's trucks. Use a Y in the Camanche stock filler to fill both tanks. Use the rear tank only for your heater

 

 

Do you have a picture of one installed in that location?

 

Looks kinda large, but hell if I know without scale:

https://www.rockauto.com/en/moreinfo.php?pk=4303848&cc=1122185&jsn=13916

 

Here's the Blazer/Jimmy one that I figured would be worth a shot, mostly because it's a shape that looks more likely to nest into the existing X crossmember:

https://www.rockauto.com/en/moreinfo.php?pk=17424&cc=1164709&jsn=14023

 

Third edit, if it's just for a heater a universal boat tank might be big enough...  Or one of those cylindrical hot rod tanks that Speedway sells like this:

https://www.speedwaymotors.com/Black-Poly-Fuel-Tank-12-Gallon-10-x-36-Inch,34441.html

Either would likely require cutting an access hole/door to fill from inside the bed...  Might not be your style.

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If it's weak, then make it STRONGer. If it's hot, then make it COOLer. If it doesn't fit, then MODify it. 

 

:usaflag:

 

Only research I need to do is setting up the fuel switch to 'toggle' in operation. Reading on a few 'in service' designs should be sufficient. This'll be an easy mod I believe.

 

Yes, I'll prob waste some time seeking a parts MJ for the tank, straps/J-hooks and hook 'bosses' for the J-hooks. Goes without saying. It's 30 yrs old. Hahah. Prob fab my own skid plates unless they're inexpensive aftermarket. 

 

It'll be setup like a pre-runner, so I'm mounting the two matching spares off the rear of the bed. No need for an under-bed spare, though this one still has a working cable system. :)) Giving that to my Brother for his MJ. 

 

 

By the way, I use to rebuild autos/vans and trucks (Toyota to F-250's) for a living. Any mod is possible. :holdwrench:

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You can just buy a tank and straps new, and they're cheap.  I'd just make the J bolts or buy the XJ ones that are available.  The only thing that isn't readily available is a sender/pickup setup.

 

That said, I wouldn't use a MJ tank.  I hate steel tanks and would try a Dakota one first if you're dead set on putting one on that side.

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I have been looking at doing something similar but my plan is to use an XJ fuel tank, sending unit, skid plate, and fuel door and just weld it in place behind the rear tire and mount the tank where the spare tire was mounted. Still trying to figure the specifics but I have the parts now and will post the pictures when it is done

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