Removing the gas tank and fixing hole, FZJ80

[Brian894x4]

Yes, the pressurized part does bother me, but I think I have solved.

I plan to seal the tank with pematix tank sealer, which is impervious to gasoline and should fix the hole itself. Then I plan to cover that with Permaix No. 1, once the tank sealer dries. The Permatix No. 1 is a hard sealant when dry. When I close the floor up, this will keep pressure on both the tank seal and permatix no. 1. There's really no way for it to come loose. Either one of these sealants probably would work by themselves, but by doubling up and having pressure on the repair, it should work.

I'd be more worried if I was patching a hole on the bottom or side or an area where nothing was holding the patch down in case it decided to blow out.

 

[UK4X4]

Instead of sealer over the top, use a small steel or aluminum plate about 2" round.

Put on the tank sealer, the plate over the top and a large weight on top of that till dry.

A bit like a tyre patch

 

[powderpig]

I replaced a fuel tank not too long ago. It really is not that hard. But if I remember right I had to remove the drive line to have more room. I can lay under my truck tomorrow and see what I remember what I did.
As for a fix, Welding is the way to go for permanet fix, unless you find a used one for a better price. I had dented mine on a trail and could not pop the dent. I found a used one for $75 and swapped them out. The hoses at the rear were the biggest pain. Any how good luck on your choice.

 

[IZZYDUSIT]

Brian-
first- doo-doo occurs!!!
secondley, cheap is expensive!
I will not bore you, but do yourself a favor and do it right-take the gas tank out and take it to a radiator shop where they will clean the tank, and than weld it right.(water fill method)
I know of a radiator shop owner in Glendale AZ who died
when a gas tank blew up as he took a shortcut to a fuel tank repair.
we all want to save a buck, and have a great appreciation to the DIY'er, but when it comes to safety matter nothing is worth messing around with.
I've been in the automotive repair business for 30 years and I have seen some horror results of a makeshift repairs.

 

[Brian894x4]

Thanks all for the advise and I appreciate the suggestions for removing the tank and doing it right. I would probably be making the same suggestion to someone else.

Thing is, there's a bunch of reasons why I think this repair will work and will in fact be overkill. Even if I pulled the tank, short of welding it, I'd be doing exactly what I'm doing with the tank in place.

The hole is extremely small and on top. It's smaller than the tip of a pen. I would say about or less than 1/16".

This is what I've done and my plan. I've opened up the floor hole to allow me to work. I cleaned the top of the tank through this hole. I then used some Permatex gas tank sealer, which looks like hard apoxy. This alone should effect a repair, but I'm taking a few extra steps.

One that apoxy dries completely, I'm going to put Permatex No. 1 (gasoline impervious and hardens when dry) and place this over the repair and fill it up to the top of the floor (there's only about 1/4" gap).

Then once that dries, I will have a cover on the floor that fits over the floor and puts pressure on the repair.

I just can't see how that repair would fail. If had multiple holes, which I don't thankfully or a larger hole, I would think twice about this plan and remove the tank. But I honestly think this will do it.

I guess we'll just have to see. I would be interested to know if anyone has had this fuel tank repair epoxy from Permatex ever fail on them?

 

[RoundOut]

Reading this thread reminds me how lucky I was that when I mounted my flashlight with quickfists, just inside the door below my drivers' seat, I missed drilling through my fuel line by about a quarter inch. I had no idea that the fuel line ran behind the floorboard there. A quarter inch could have meant a pine box. Whenever I put my truck up on the lift and check for loose things, change the oil, or whatever, this near miss is remembered.

I feel for you, Brian! Good luck with your repairs.

.

 

[Brian894x4]

Fuel tank pressure or vaccum?

For some reason I was thinking that the tank would be under pressure from the inside out and working my repair on this assumption, but obviously, this can't true, or fuel and vapor would come out every time you opened the filler.

In fact, the fuel tank is not under pressure, but under vaccum, right?

The vaccum I assume is simply from the fuel level lowering, but no air being allowed to get inside. The lower the tank, the higher the vacuum...right?

So, the problem of blowing or in this case, sucking in the repair is still an issue. But the problem of potentially blowing out fuel and vapors is less likely now.

So, I figured the hole is about 1/16" or less. So, that means I could fit 256 holes that size in a square inch. Why this is important is to show just how little pressure or vaccum is being exerted on that hole. I could have this all wrong, but whatever the fuel tank pressure or vaccum is, you have to divide that by 256 to get the actual pressure being exerted on the repair.

For example, if the fuel tank was pressurized (since my feable mind can calucate pressure easier than vacuum) to 34psi, the actual pressure on being exerted on the repair point would only be 2 ounces of pressure. Which is definately not much, and I'll bet the vacuum/pressure of the tank is far less.

I could have this all wrong as math is not my strong point at all. Does anyone know what the typical vacuum/pressure is inside a fuel tank, or at least the maximum vacuum? It can't be too much or the tank would collaspe in on itself. At the very least the rubber hoses would collasp, yet they don't, and the cap would be hard to get off, so vaccum must be minimal. Which means the affects of pressure/vacuum on this repair would be VERY minimal.

So with that in mind, this repair seems far safer than I first thought. Heck, chewing gum or duct tape would probably fix it just fine, not that I'd use that....

The epoxy I have is impervious to gasoline which would be critical.

 

[Life_in_4Lo]

yikes, that is unfortunate but a good reminder to check before you drill!

anyway, desertdude's solution sounds quick n easy. that is what i'd do

 

[RoundOut]

Positive or Negative pressure?

Are gas tanks typically operating under vacuum?

I am NO EXPERT on this, but intuitively, here are some thoughts...

I have four 5-gallon red plastic gas cans that I typically store 20 gallons of fuel in for emergencies, along with a generator with a 7-gallon tank on it. In the summer, the cans always look like they are about to pop, becuase the vapor pressure of the gasoline is "light" enough that it evaporates, expanding the cans slightly. In the wintertime, though, the gasoline tends to contract, causing the cans to look a bit "indented" on the sides. This is partly from the expansion and contraction of the liquid, but also from the vapor in the can's vapor space -- never fill one full. There are a couple of things that surely affect the evaporation of a liquid, including temperature, pressure variation from the liquid's container and ambient outside pressure, and agitation.

The vapor pressure of gasoline typically causes an idle tank to have positive pressure in warm temperatures, hence the emmission controls issues that are common on gas tank caps.

However, I can imagine a vehicle driven in colder weather on smooth roads could easily create a vacuum in the gas tank as gasoline is consumed by the engine.

So, I bet that sometimes the tank is in positive pressure (i.e. warmer days idle, or driven on bumpy roads such as when wheeling) and other times the tank is in a vacuum, colder climate and driving on smooth surfaces.

Any scientists wish to chime in here?

 

[AndrewP]

My 80 always seems to be under slight pressure when you pull off the cap. I'm sure due to the vapor pressure of the gasoline. In fact, part of the smog test here is to put the cap under pressure and make sure it holds.

 

[adventureduo]

Sorry to hear this happened Brian. Hope you get it sorted out and fixed in no time man.

You think that's scary, try cutting the fill tube with a hacksaw to install a aux tank!!! One spark your umm... kind of dead.. or wishing you were! Needless to say i cut very slowly, one stroke at a time!

 

[dieselcruiserhead]

I have a spare tank for a FZJ80 if you are interested out of a '93. I would sell it darn cheap and include fuel pumps / senders etc... The only thing is a friend expressed strong interest in it this weekend, if he doesn't come through I would gladly let it go... I was thinking something like $150 with everything, hopefully $50ish for the ride if we are lucky...

 

[Desertdude]

You think that's scary, try cutting the fill tube with a hacksaw to install a aux tank!!! One spark your umm... kind of dead.. or wishing you were! Needless to say i cut very slowly, one stroke at a time!

Gee I did mine with a sawsall to get it over with quickly...

 

[adventureduo]

Gee I did mine with a sawsall to get it over with quickly...

hahhahahah you're braver than I! Im too paranoid to do it that way. Instead i took like 1 hour of slow cutting.

Notice the extinguisher ready to go lol




Brian, i would totally go with Dieselcruiserheads tank if you can swing it. That would be ideal.

 

[AndrewP]

I too was paranoid about the cut. To avoid a flaming death, I actually disconnected the fill pipe and vent from the tank, then capped the tank, then cut the pipe. No drama that way.

The old rubber bits were hard and dried out and so were replaced with new and pliable Toyota.

Brian-I think Andre's offer of the fuel tank is a good one, and the way I would go if you don't want to get yours welded. If you think about the thousands you've spent on mods, sending a couple of hundred to have this fixed by a professional does not seem that bad. A half-assed body repair is fine, it isn't mission critical, but a fuel tank seems pretty important, and potentially dangerous.