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Discussion Starter #1
Here's the deal, my YJ with only 68K original miles spent 10+ years untouched in a field before I bought it a month or so ago. I've got it running perfectly now, with one exception. When the gas level gets below 1/4 tank, it starts occasionally sputtering or dying, getting worse as the fuel level goes down. Fill her up and she runs perfect again, till the fuels goes below 1/4 tank again. Seems to be a sure sign of water or other contamination in the fuel. So this brings up a couple questions:

Where is the fuel pick up in the tank? Does it float with the fuel level? Seems lf it was always at the base of the tank, where water and other contamination will collect, I'd always have the problem rather than just when gas is low.

Should I run the tank down then drain the last couple gallons to get rid of the contamination? If so, what's the best way to do that? Is there a drain valve on the tank somewhere?

Or should I just run a few more tankfulls through it, and eventually the bad stuff will get sucked out?

Thanks
 

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I dont think you can go wrong with draining the tank and even dropping it and cleaning out any trash.
You could try a fuel additive or even 91% rubbing alcohol to get any water out.

Sent from my SM-G930U using Tapatalk
 

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10+ years in a field is not good for any fuel system. Personally, I would drop the tank and clean it out by what ever means it takes to actually get into the tank to see what's going on. The newer tanks have an in-tank fuel pump that has a hole big enough to remove and reach in to clean things up. At the very least, put some Sea Foam (or some other type of water remover) in the tank to break thing loose and get thing flowing. If there is any water in the tank that does not get removed, it will rust through and cost you a new tank.
 

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10 years sitting = Drop the tank in my book.

Doubtful, but if there is an aftermarket pump/sender, some come with a length of hose that attaches to the pickup at the bottom of the tank that has fallen off or developed a crack in it reducing the suction, if you have EFI it could be pumping air with the fuel to the rail.

Either way, Like Stephen said, couldn't hurt to drop the tank, Also a good time to redo the filler hoses and fuel lines under there and get it out of the way....
 

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Maybe it’s running bad because you’re out of gas and the gas gauge is incorrect how many gallons of gas does it take to fill up after it starts running bad
 
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Drop the tank and replace the sender/ pickup

I'd bet that solves your problems

99% if it was water in the tank you would have problems no matter what level the fuel was
 

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Maybe it’s running bad because you’re out of gas and the gas gauge is incorrect how many gallons of gas does it take to fill up after it starts running bad
I thought of this, but upon further reflection, if it were my Jeep, I'd drop the tank. Run it low on fuel then drop it. Even if there's 10 gallons in it, dropping the tank isn't really an issue because gravity is on your side.
Throw the gas away or use it in your lawn mower.

The fuel pickup should be a mesh filter (sock) laying on the bottom of the tank.

Once you clean the tank and inspect the sending unit (and the in tank fuel pump if you have one) reinstall it while it's empty. Once the tank is reinstalled, if you put a known quantity of fresh gas in the tank (say 10 gallons) you can check the accuracy of your gas gauge.
Have new hoses and gaskets handy before dropping the tank. Depending on which engine you have and the year of your Jeep, I suggest that you have new vents and roll over valve with grommets handy also.
Again, depending on the year of your Jeep and how it was ordered at the selling dealership, you may want to check to see if it's had the 20 gallon mod done.

Reinstalling the gas tank is a little easier if you use a cargo strap to pull the tailpipe aside.
You most likely have a plastic tank so rust shouldn't be an issue with the tank itself, but the sending unit and perhaps the fuel pump could be an issue. That's why I'd drop the tank, just to be sure it's clean and the guts are in good condition.

Good Luck, L.M.
 

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If you drop your tank, go ahead and replace the rollover valves and all the fuel lines. Doing it right one time is always cheaper and less aggravating than half-assing it and regretting it. Also, dropping your tank will allow you to inspect the bottom of the tub for rust.
 

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Discussion Starter #9
Thanks all. Pretty unanimous here, drop the tank! I'll add that to the list of winter shop projects on the Jeep.
 

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Even if you add Seafoam or some other additive and the sputtering quits, I'd still drop the tank and check the sending unit (and fuel pump if your Jeep is equipped with an in tank fuel pump).
And of course, replace all the related valves, gasket and hoses.
There are pics on this forum of fuel pumps that are so corroded that you'd wonder how they even worked enough to leave the driver stranded. Usually in Jeeps that sat for extended periods of time.

Post some pics of what you find so the next guy will have an idea of what he might find.

Good Luck, L.M.
 
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