TJ / LJ Fuel Fill Fix

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TJ / LJ Fuel Fill Fix

Postby tobyw » Fri Mar 25, 2022 6:26 pm

For those of us with a TJ / LJ, particularly the later model years 2003-2006, there is a common issue wherein the seemingly simple process of filling with fuel is infuriating at best. This is because the fuel either splashes back up and out the filler neck, or the pump continually clicks off so you simply cannot add fuel with any speed whatsoever. I'm talking speeds like your California-transplant neighbor's Prius recharge time here folks, and that simply won't do...

For literally decades, there have been some common "fixes" to try and alleviate the problem(s), all with varying levels of success. But, much like the deplorable death wobble, the band-aid fixes and hipster life hacks simply aren't the right answer. The correct fix is shockingly simple, but does require dropping the tank.

The actual problem is that over time, the anti-splash back valve begins to stick. When it sticks in one position, it blocks the inlet flow of fuel from the filler neck. When it sticks in the other position, it allows the fuel to splash back up the filler neck when the tank gets full, which is actually what it's there to prevent in the first place :roll: Anyhoodles, let's get this fixed.

Step one is to drop the tank. My strong recommendation is to get the tank as empty as possible, as any amount of fuel in the tank makes it that much more difficult to maneuver and that much more likely to leave you with a stinky hand and arm from being submerged in fuel. More on that later.

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With the tank down, spend as much time as you can cleaning the top of the tank, particularly the area around the fuel pump assembly retaining ring. You want this surgically clean before you pound the ring off and open up the tank. Do as I say, not as I do :oops:

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Once its all clean, take a hammer and punch and knock the ring off so the pump assembly can be removed:

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Here is where you really want to have as little fuel in the tank as possible, because you now have to reach aaaaaalll the way into and across the tank, to the bottom of the fuel filler neck. What you are looking to do is release the anti-splash back valve from the filler neck, and it's held on with 4 pressure tabs that you simply need to depress one of, and then wiggle the assembly until it pops off. It's sort of like trying to break a carrot in half with one hand... Here is a picture from inside the tank, looking at the bottom of the fuel filler inlet (the one that appears to be glowing) where the assembly was attached:

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Here is the assembly after removal from the tank:

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After pulling the plunger and spring out of the valve body, you can see the signs of wear on the guides as well as sediment trapped in the valve body, both causing issues with the free movement of the plunger within the valve body:

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So the fix is to simply clean the valve body of any debris or sediment, and then ever so slightly grind away a little bit of meat from the guides on the plunger body. It takes no time at all with something like a flapper disc on an die grinder or Dremel, but could take a few minutes by hand with sandpaper or a file. Regardless, the idea is to create a little clearance between the plunger and the valve body so the plunger floats up and down freely as intended. It's likely that over time the plastic of the plunger swells and causes it to drag within the valve body, and in my case I was also fighting sediment buildup from who knows when.

Anyhow, after cleaning and a light sanding, the plunger does it's thing perfectly. Simply click the assembly back onto the filler neck inside the tank and put the tank back into the Jeep, and enjoy hassle-free fuel ups like you did when it was new(er). 8)
Yep, I've wheeled one of those, too...

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Re: TJ / LJ Fuel Fill Fix

Postby Roman » Sun Jul 24, 2022 7:22 am

Still need to make time to get this fix done...

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Re: TJ / LJ Fuel Fill Fix

Postby TJDave » Sun Jul 24, 2022 5:48 pm

Back when I used to scour the TJ build forums, I thought I read about using an older Chevy truck fill hose. Can't remember the year or model.
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