Stock Gas Tank to Water Tank?

[fyrfytr1717]

Hi all, new to the forum and had a question regarding my trailer build up. I'm starting out with the rear half of a Jeep MJ Comanche and I'm turning it into an off road camping trailer. It's going to be more for hauling camping gear behind my XJ as opposed to being a full on expedition trailer.

I apologize if this has been covered, but my searches have thus far come up empty. My question is this: It still has the stock fuel tank, fuel pump, filler neck, etc. in place and I'd like to put it to use. I'm considering the following options (in order of preference).

1. Convert it into a water tank. Drinking/cooking water if at all possible, but if not, then just water for washing dishes and for other use while camping.

2. Use it as a fuel tank. I'd like to use the fuel pump for off loading the fuel, but I think it may not put out enough volume to make it very useful.

3. Ditch the tank all together.

I plan on mounting 4 Jerry cans on the tongue just in front of the bed for fuel and/or water depending on how I can best utilize the stock tank. So what would be my best option here?

 

[fyrfytr1717]

Here's what I'm starting with:

And here's what I'll be towing it behind:

Thanks for any input!

 

[Peter_n_Margaret]

Water will rust it quickly....
Best/quickest way to pump fuel OUT is to pump compressed air IN (carefully....don't give it tooooo much).

Cheers,
Peter

 

[spencyg]

This sounds like a pretty bad idea to me...I'm not sure I'd ever be convinced that ALL of the fuel was out of the tank. Gasoline has a way of permeating into the surface structure of some metals....I wouldn't risk it. Pony up $150 for a marine grade water tank....it isn't worth risking your health and the health of your friends and family to saving a couple bucks.

Don't do it.

Spence

 

[TooeleCherokee]

I just finished building my trail trailer out of a 86 2Door XJ. That said I kept the fuel tank in the rear as a fuel tank. the fuel pump puts out enough volume to transfer the fuel in about 20+Minutes. Not bad as a normal BS stop is about that long and lunch is usually longer for me. If you run the fuel tank back there you need to put some more weight up front to counter the fuel in the rear.

 

[ntsqd]

X2
Spence beat me to it. Gasoline does permeate steel and you will not likely ever remove trace gasoline from the water.

Though it does work, moving fuel with compressed air is not a good idea. Such fueling systems are outlawed, with good reason, in every racing sanctioning body that I know of.

 

[Mayne]

X2
Spence beat me to it. Gasoline does permeate steel and you will not likely ever remove trace gasoline from the water.

Though it does work, moving fuel with compressed air is not a good idea. Such fueling systems are outlawed, with good reason, in every racing sanctioning body that I know of.

Please explain? Only ask because the outback fuel pump I have runs on air. It's all brass fittings, so no spark, but this is the first I've heard of this. I don't care to be a roman candle.

Mayne

 

[ntsqd]

The problem with a pressurized fuel tank is that the whole system and the tank is pressurized, not just the hose and hard line between the engine and the fuel pump. That is a very large volume to have under pressure. Since fuel tanks are rarely made to pressure vessel standards, their springing a leak was not uncommon. Any leak in such a system nearly always sprays fuel, even those in the air system. Liquid fuel is hard to light, atomized fuel is not.

It isn't so much that it can't be done. It is that it is rarely done well enough to be safe. And if it is done safely, then it is too heavy for a race car, and likely unnecessarily heavy for an Overlander.

 

[rezdiver]

you should never ever use a fuel tank for use with clean water, you will never ever get all of the fuel residue out of the tank, the steel is porous and absorbs contaminants, it will leach out for most of its life even if it is acid cleaned. even if you use it for cleaning your dishes you will be passing on contaminents and fuel residue in small amounts.

just as an example i had a nice pair of high pressure CNG natural gas tanks that were cleaned and acid washed, i wanted to use them for pressurised air. the company that does pressure testing for cylinders said they would not touch it with a 10 foot pole no matter how clean it was as they did not want to cross contaminate their gear and water hydrotest equipment with the Natural gas residue that leaches out of the steel for the rest of its life.

 

[Maximus Ram]

my .02 worth

either keep the fuel as fuel or ditch it and install a proper water tank.

 

[Mayne]

The problem with a pressurized fuel tank is that the whole system and the tank is pressurized, not just the hose and hard line between the engine and the fuel pump. That is a very large volume to have under pressure. Since fuel tanks are rarely made to pressure vessel standards, their springing a leak was not uncommon. Any leak in such a system nearly always sprays fuel, even those in the air system. Liquid fuel is hard to light, atomized fuel is not.

It isn't so much that it can't be done. It is that it is rarely done well enough to be safe. And if it is done safely, then it is too heavy for a race car, and likely unnecessarily heavy for an Overlander.

Makes sense. Don't know why that never occurred to me, I'm usually pretty common in the sense dept.


Thanks

Mayne

 

[ntsqd]

Something that I forgot to include: In a race car consider the possibilities after a crash......

 

[fyrfytr1717]

Wow, thanks for all the quick replies folks! I appreciate the supporting info beyond just a simple yes or no. I always like to know the "why" behind the answer.

I was kind of assuming there would be an issue with residual fuel in the tank. I had not however considered the rusting issue. That pretty much rules out using it as a water tank.

Sounds like using the stock gas tank for fuel storage would be OK. I'd like to use the fuel pump for transfer as I wanted to avoid the expense of buying a commercial transfer pump. Speed is not really that important to me, but a buddy of mine told me it took his fuel pump (not on a Jeep) about 45 minutes to fill a 5 gallon bucket when he was emptying his tank. Maybe his fuel pump was failing? TooeleCherokee, when you said 20+ minutes, was that to fill a Jerry can, or to empty your whole tank?

 

[R_Lefebvre]

Is the fuel pump being discussed for a carburettor, or fuel injection? You can get some very high flow fuel pumps for fuel injection if needed and you don't mind spending a little money.

255l/h for just a little over $100. That equates to a little more than 1gal/min.

 

[4xdog]

Maybe a dumb question, and I really ought to double-check my 1988 XJ out back to be sure, but isn't the fuel tank in a Cherokee of this period made from fluorinated low density polyethylene, not steel?

As a chemist, I could imagine the idea of converting a LDPE tank from gasoline to water to not be impossible, although a little difficult. I might take a LOT of soaking, and ultimately maybe a new tank in the stock location, but this doesn't seem like a completely crazy idea.