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Unread 03-21-2008, 08:41 PM   #1
iflyabeech
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1999 XJ Cherokee 
 
Join Date: May 2003
Location: Corpus Christi, Texas
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99 XJ Fuel tank capacity mod

I replaced my fuel tank last week, and while I had it down, I thought I would try to up the capacity in my fuel tank as some have done to older cherokees like this: http://www.go.jeep-xj.info/HowtoFuelTank.htm

Although my tank is a little different and plastic, it still worked pretty much the same as the older mod. I bought a piece of blow-by hose (the same size as my vent line) which was already bent into a 90 and a hose clamp with a wing nut on it so I could hand tighten it. I fastened the hose to the vent tube inside the tank and positioned it so that it was almost at the top of the tank. I poured 2 gallons of gas in the tank, then filled up with 22 gallons of gas. That makes 24 gallons!

I brought along a gas can with 2 gallons of gas and drove until the tank was plumb empty and I made it exactly 401 miles on the tank! Almost 230 miles of that was spent driving over 80 MPH on the interstate, with some city driving mixed in as well. I figure 16.7 MPG. Should be a little better if I don't drive so damn fast!

I couldn't be happier that I don't have to fill up as often! My gauge sits on Full for a long time (I think it was above F for 150 miles or so, but the E certainly works. I ran it empty so I could tell exactly how far I could go on the gauge since I changed the fuel pump assembly.

I thought someone else may want to mod their 99 as well. IT sure makes it easy to find the cheap gas!

Hopefully this weekend I can add my Quadratec HD springs to end the sagging rear end problem!

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1999 XJ Cherokee SE 4dr 4x4
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Unread 03-21-2008, 10:27 PM   #2
HeepToJeep
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That's definately a nice modification, those extra miles between stops really add up. I read where another guy did the same mod but he simply curved the vent tube up by hand quite a bit then used stork needle nose pliers to finish curving it up until it touched the tank after he had it slipped back in. I think his method sounds a lot easier and more foolproof since a soft line extension may sag over time. (Although unlikely)

Wm
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Unread 03-21-2008, 10:31 PM   #3
iflyabeech
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Its possible for the soft hose to sag over time. The guy on go-jeep said his did, but I don't think he used as sturdy of a hose as I did. The blow-by hose I used was preformed with a 90, and it was pretty sturdy. I would prefer something even harder, but I really didn't have any other materials.

What I did doesn't get any easier though. The Hand tightening hose clamp was nice. All you do is slip the hose on and tighten the clamp down!
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1999 XJ Cherokee SE 4dr 4x4
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Unread 03-21-2008, 10:57 PM   #4
davevolk
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What is the Maximum Capacity of the '97 up fuel tanks?

Hello,

Just curious. What is the maximimum capacity of the '97 and newer tanks? I believe the manual states 20 US gallons. I have a 2001 Cherokee and have routinely put 20 gallons in at the pump when it's a bit below E. Based on that is the capacity slightly more than 20 gallons? I've been trying to get some accurate gas mileage readings and it seems to vary quite a bit. I usually try to fill the tank till it's almost coming out the filler neck. Just wondering if anyone had measured the total stock capacity?

Thanks,

Dave
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Unread 03-21-2008, 11:01 PM   #5
the_weirdo
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The stated capacity is 20 gallons. I can usually get a little more in mine if I pump it slow.
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Unread 03-22-2008, 07:37 AM   #6
iflyabeech
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Normally, I used to only be able to put in 17 gallons. I sometimes fill up to a station where the pavement leans to the right, which serves the same purpose as the mod by keeping the vent uncovered longer. Before the mod, I was able to put 19 gallons in at this store. I am not sure what the stock capacity says, but I thought I read it was 17 gallons somewhere...
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Unread 03-22-2008, 07:47 AM   #7
fedrusion
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Stock capacity is 20. I would be worried about hot summer months when the heat will cause the gas to expand, now that you have used the extra air space ikn the tank where is it going to go. Be carefull not to fill it right to the top in the summer.
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Unread 03-22-2008, 07:56 AM   #8
iflyabeech
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True, but its always hot here in South Texas! I should have pointed out the heart thing.
But according to this, http://www.nytimes.com/2007/07/15/au...les/15GAS.html
20 gallons warmed from 60F to 90F only increases the volume .41 gallons. That amount would fit easily into the small space above the top lip of the hose.
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1999 XJ Cherokee SE 4dr 4x4
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Unread 03-22-2008, 09:04 AM   #9
fedrusion
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Just putting it out there to hopefully help someone avoid a problem. This would probably only happen if someone was in the habbit of filling right up to the top of the filler neck and then park it. If you fill up while your on your way somewhere and not just parking you shouldnt have a problem.
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1999 Cherokee 2 Door Sport (To be modified) Mine. http://www.cardomain.com/ride/2814633/1
5.5" Composite lift, Rough Country Control Arm Drop Brackets, 31X10.5X15 Dayton Timberline AT's On Canyons, 31X10.5 Firestone Destination MT's, P.O.R.C. SYE and front CV Drive Shaft, Homemade Short Ram Intake, Locked 8.25. Comming Soon: Stroker.
2000 Grand Cherokee Laredo (To be left alone) Wife's. http://i151.photobucket.com/albums/s...n/IMG_0007.jpg
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Unread 03-22-2008, 10:40 AM   #10
iflyabeech
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Quote:
Originally Posted by fedrusion View Post
Just putting it out there to hopefully help someone avoid a problem. This would probably only happen if someone was in the habbit of filling right up to the top of the filler neck and then park it. If you fill up while your on your way somewhere and not just parking you shouldnt have a problem.
Makes sense!

I just filled up with the Jeep level and it took 22 gallons from a dry tank! not too shabby, but I will try to fill up and the one with the angle more often!
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1999 XJ Cherokee SE 4dr 4x4
4.0L I6, AX15 5-Speed Tranny, NP231, Dana 30 high pinion Front, Chrysler 8.25 Rear, 3.07 gears, Quadretec HD leaf springs
http://www.thirdcoastoutdoors.com
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Unread 04-02-2008, 02:59 PM   #11
Guswut
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That's a pretty nifty mod. that beats the 500$ 37-gal tank (which I was eying as it'd be REALLY nice to be able to have that extra 20 gallons in the tank (I fill up to about 17 gallons for nearly out of gas) in the cost (a few dollars for some nice tubing and a hose clamp). I'll try it out after I run down my current tank of gas (I keep a 5-gal spare tank in the back so I can run it dry just to make sure, heh).
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Unread 04-02-2008, 06:07 PM   #12
iflyabeech
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Just take your vent hose to the store to get the right size hose for the inside. If you are going to drop the tank for this you may as well replace at least the pickup filter for the fuel pump as well. I have an extra that I will sell, but they are about $8 from the auto parts store. PM me if you want it
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1999 XJ Cherokee SE 4dr 4x4
4.0L I6, AX15 5-Speed Tranny, NP231, Dana 30 high pinion Front, Chrysler 8.25 Rear, 3.07 gears, Quadretec HD leaf springs
http://www.thirdcoastoutdoors.com
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