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Old 06-23-2012, 09:37 AM   #1
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Thumbs up 15 to 20 gallon Gas Tank Modification

This is kind of a gloat... but some of you might enjoy it...

I have owned my jeep now for a couple months and started to plan some of the modifications I want to make. I have spent a lot of time browsing web pages and one particular modification that caught my eye was to increase the capacity of the gasoline tank from 15 gallons to 20 gallons.

This might be a rehash of previous discussions on this topic, but in case there is someone other than me left out there that had not made this mod, it might ease your pain some. Not much, but some.

My jeep seems to get about 15-18 mpg. A tank lasts about 225-250 miles, so I end up stopping to fill up around 200 miles. For daily driving and short trips, this is not that significant. However, I have some longer drives planned later this year (Moab?) and coming from Texas, I might want a little more range from the tank. I know, it will take about 3 hours to go 200 miles, and that is a reasonable time to take a break, but humor me... I am male and if I can get more, I want more. Especially if it is "free."

There are a couple really good websites out there describing how to do this that have some detailed pictures. After looking at these and reading them several times, I convinced myself that even I could do this.

This started for me during a browsing session for general upgrades where I saw a replacement 20-gallon tank for like $500. I made a mental note about this and later decided to see if there were cheaper ones for sale. This is where I stumbled upon one of the modification pages describing how to do this conversion.

For those of you who are not familiar with the situation, Jeep offered a 20-gallon option instead of the 15-gallon standard tank. In reality, it is the same tank. The difference is that the 15-gallon tank has a vent tube inserted that traps a 5-gallon bubble of air at the top of the tank. If you shorten the vent tube, you reduce the size of this bubble and the tank will hold more gasoline... so this is the premise behind the modification.

I was especially encouraged by comments indicating that the mod could be made in 30 minutes or so... that one of the posters fiddled with dropping the gas tank so it took about 90 minutes. My warning here is that your results may vary; translated this means your results WILL be worse.

On a nice sunny Saturday morning, I recruited my neighbor's son to assist. We laid out tools and set about making this happen. I quickly got through the part where you remove the cover from the rear tire well to the fill tube. When it came time to disconnect the fill and vent tubes is where things went sideways.


We looked at dropping the tank, but had issues due to the exhaust line blocking the passenger side of the tank. I think that during the manufacture of the jeep, they put the gas tank on the frame before they lowered the body in place. Hence, the hose clamps are on the top at an angle where you cannot easily get a wrench, pliers or socket in there to loosen the clamp... or when you do, there is no room to move it.

I take great pride in my work and abilities. So I found this to be quite frustrating. I also try to set a good example for my neighbor's son by limiting my use of foul language around him. After about 6 hours where both of us were taking turns trying to loosen these clamps, he was about as adept in the use of some of the more colorful reserved language phrases in the English language as I am.

I convinced him that using a torch to burn the hose off the tank was not an option... especially since there was a small quantity of gasoline still in the tank. (ok, it was more like him convincing me...) Finally, in total frustration, I took a pair of chanel-lock pliers and grabbed the hose next to the tank, and twisted. The hose slipped around and we were able to remove the clamp.

We were on our way. The vent tube came out and we cut it down to the recommended length and reinserted it. Everything went back together pretty quick. The hose clamps are now positioned in a more humane location. All said and done, it took about 7 hours to complete the mod.

Anyway, my neighbor's son rode with me to the gas station and I let him pump in the gas. I don't know who was smiling bigger as the pump went passed 15 gallons on up to almost 19 gallons. On the way home, I took the opportunity to explain that there were right and wrong times to use colorful language... I didn't want to be seen as a bad influence just in case I needed his help again.
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Old 06-23-2012, 10:32 AM   #2
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One tip on those stupid hose clamps is to loosen the nut that hold the tank in it will drop the tank enough to get to those clamps that r factory installed that way.

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Old 06-23-2012, 03:34 PM   #3
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Quote:
Originally Posted by Jeep_Monkey View Post
...For those of you who are not familiar with the situation, Jeep offered a 20-gallon option instead of the 15-gallon standard tank...
Also for those not familiar with the situation, this is true for 1991 & up.

1990 & older, the 15-gal tank is actually 15-gal.
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Old 06-23-2012, 05:42 PM   #4
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Also, you might want to add that your (now)19 gallon tank will still believe it's a 15 gallon tank when it comes to how your gauge reads. Get a 19 gallon tank sender/gauge and you're set.
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Old 06-24-2012, 07:00 PM   #5
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Smile

Good comments folks. I sometimes am short sighted and can only see my little corner of the woods, so this mod only works on a limited number of YJ model years, including my 1994.

When I filled the tank, the fuel guage was pegged high for about 100 miles, then it started reading like a 15-gallon tank. I drove it for about 330 miles and put 18 gallons in the tank... and it was reading around 1/8th tank. I know from experience that "E" really does mean empty, so this is about as close as I probably will push it. Just in case, I usually reset my trip odometer each fill up, so I can estimate if my guage is reading right or not.

I looked at the cost of a new unit that would give 20-gallon range indication, but decided I could get by without spending that $200 plus right now. That, plus I need to let the colorful language ripples kind of settle out around here before I disturb the waters again.

I certainly appreciate folks sharing ideas and input like this. It makes enjoying my jeep that much more special.
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Old 06-24-2012, 07:44 PM   #6
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Good thread.
I had been actively pursuing this mod until I discovered it did not apply to my '90.
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Old 09-12-2012, 01:10 PM   #7
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how much do you cut off?
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Old 09-12-2012, 01:25 PM   #8
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On my 1990 YJ my fuel gauge goes from full to empty but only uses about 10 gallons. So should I assume that my sending unit isn't reading correctly and that at empty I probably still have 5 gallons?
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Old 09-12-2012, 02:08 PM   #9
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Quote:
Originally Posted by DARKSLAYER56 View Post
On my 1990 YJ my fuel gauge goes from full to empty but only uses about 10 gallons. So should I assume that my sending unit isn't reading correctly and that at empty I probably still have 5 gallons?
You most likely have 7gals. left (2 reserve) but I wouldn't push it.
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Old 09-13-2012, 04:57 AM   #10
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Quote:
Originally Posted by Beach-Bum View Post
how much do you cut off?
I cut a piece about 2-2.5 inches and shoved it back into the tank vent pipe. I think this was to help keep the vent pipe from collapsing when you clamped the vent hose that runs from the tank to the filler spout back on.
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Old 09-13-2012, 05:04 AM   #11
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By the way, as an update to this thread, I finally took my 94 YJ out on a road trip over the Labor Day weekend. I had it loaded up similar to the way I plan to travel out to Utah next week, including 2 5-gallon jerry cans of gas. Having this "insurance policy," I let the gas gauge drop to E then started hunting a gas station.

It was sputtering as I coasted to the pump. I put in 20.25 gallons, so I am still very pleased with the results.
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Old 09-13-2012, 01:10 PM   #12
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well it looks like everything worked out for you, way to go!!
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Old 09-13-2012, 03:58 PM   #13
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Picking up my jeep today. Want to try this before I leave for Philly Wednesday
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Old 09-13-2012, 05:37 PM   #14
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My '93 fuel gauge sits at Full for about 100 miles and then it drops like a rock and by 150 it shows 1/4. I'm curious if the PO did this mod but haven't had a chance to test it to see how far it can go before truly being on E. One of these days I will carry a fuel can with a few gallons in it and run it as far as I can. Any issues with running it until she stops dead?
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Old 09-27-2012, 06:16 AM   #15
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^^ scroll up 10 posts haha, I am going to do this next week. Awesome idea thanks.
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Old 09-27-2012, 10:41 AM   #16
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I did this a while ago. When I fill up the gauge buries itself into the full area. About five gallons later it starts to drop. It then reads accurately from full to empty. One thing I did need to get that hose out was needle nose vise grips.
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Old 12-14-2012, 05:22 PM   #17
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I don't mean to hijack this thread. I've been reading tons of Wrangler stuff on this forum for a few months but never contributed. I recently did the fuel tank mod to my 1992 YJ thanks to the posters here. It seems the common problem people face are the discrepancy with the gas gauge when it's done. Here is what one person did to fix it. They had information to modify the sending arm with photos. I found a lot of good information that people share on this forum so here is a small share that I found.

Jeep Wrangler 20-gallon Gas Tank Conversion

GREAT FORUMS
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Old 12-14-2012, 07:00 PM   #18
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Oh and you have to scroll to about mid way to get to the sending unit part.
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Old 09-15-2014, 09:43 AM   #19
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Did this mod. Takes less than an hour. The tube is a bit of a pain to get out.

Here is the video:
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Old 09-28-2014, 06:46 PM   #20
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awesome!

thanks!

love learning new sh* about my ride!
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Old 09-29-2014, 12:57 PM   #21
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This mod has been on my radar for a while and plan on doing it when I add a rear bumper/tire carrier, maybe in the spring. I have this link to add to the discussion.

YJ Gas Tank 15-to-20 Gallon Conversion

I'll throw in an update on my results.
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Old 09-29-2014, 02:32 PM   #22
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I did mine when the tank was out to replace fuel pump. I replaced the sending unit with a 20 gallon so my gauge is fairly accurate. I still don't go below 1/4 tank, just in case.
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Old 09-29-2014, 07:21 PM   #23
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Quote:
Originally Posted by TigWizard View Post
I did mine when the tank was out to replace fuel pump. I replaced the sending unit with a 20 gallon so my gauge is fairly accurate. I still don't go below 1/4 tank, just in case.
Im still running the factory 15 gallon sending unit. It now takes a while to come off the full mark. So far it seems to have the same accuracy as it did before. I just filled her up a few minutes ago because the needed was just below 1/4 tank. I squeezed 17 gallons in it ... close enough for me. With the extra capacity it hurts the pocket a bit more to fill up. But... I do go a lot farther between fill ups.
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Old 10-02-2014, 01:01 AM   #24
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I did this conversion to my '95 a year ago and should have done it 10 years ago when I got the Jeep. I just left the 15 gal sending unit in there and watch the gauge, like I should do all the time, and wait until it's about 1/4 tank and fill back up. I couldn't see the need to spend $$ on a new sending unit.
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Old 10-02-2014, 05:02 PM   #25
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Great info here...THX! My next project!
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Old 10-06-2014, 09:39 PM   #26
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Hey .. My video I posted isn't working. I'll just drop a link to the easy mod vid

15-20 Gallon YJ Gas tank convert
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Old 03-20-2015, 10:06 AM   #27
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Might have to try this with my 06 TJ. I did hear the tank is smaller but haven't verified that yet. Can't hurt to try since my Jeep never shuts off the gas pump anyway.. wont hurt it anymore if I break it hahaha.

EDIT: looks like I don't need too.. hmm Gas light comes on with 4-5 gallons left. guess I just don't run it dry enough.
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Old 03-20-2015, 11:17 AM   #28
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The sender in my '87 never worked right. I always reset the odometer and filled every 200 miles.
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Old 03-20-2015, 08:24 PM   #29
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Quote:
Originally Posted by Fishb0wl View Post
My '93 fuel gauge sits at Full for about 100 miles and then it drops like a rock and by 150 it shows 1/4. I'm curious if the PO did this mod but haven't had a chance to test it to see how far it can go before truly being on E. One of these days I will carry a fuel can with a few gallons in it and run it as far as I can. Any issues with running it until she stops dead?
I had a 92' that was reading all kinds of crazy levels left...so I had to run it dry with a gas can in the back. Found out fuel sending unit was bad and it said a little less than half tank in it when in fact it was empty.
I poured the 3 gallons from the gas can. And it started right right up. I wouldn't do it on a regular basis.
I plan to do this on my current '94
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Old 04-02-2015, 09:42 PM   #30
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Finally did the mid and it was so easy. I was actually doing something else on my jeep regarding the 4x4 issue that I had. Then the tools were already out and thought what the hell I'm out here and remembered this exact thread and how I saw a vid link from one member on the forum. It took me like 20 mins.
I didn't take the gas cap filler off. The only I did was remove the vent tank tube. Tools were needle nose pliers flathead screwdriver n of course some WD40 just to loosen up that clamp.
I didn't filler up yet but can't wait to see if I do get 20 gals.
I'm Very glad I glanced over this this thread.

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