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While I am not positive about the breakdown I know that at least genright splits the years between '04 and '05 which would lead me to believe that there are other differences in the fuel tank that would preclude you from using an earlier tank without making other modifications. I think the fuel line connections are different and fairly certain the fuel pump itself is not compatible with the earlier tank. So while you could make a swap to an earlier tank it would be far simpler to drop the original tank and fix the valve inside rather than replace the tank with another.
Thanks.

It figures that they would probably change fittings, sizes, locations, etc, when they re-configured.
 

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I had the GM hose sitting on the shelf since November. I read all the threads about the fill up issue. In the end I decided to cut the GM flapper valve out and install it in the OEM hose.

Having and LJ made the hose removal easier too. I decided to install the valve from the bottom up. I used a large zip tie to keep the valve from shifting. The reinstall was easy. The Jeep does not need fuel yet. I’ll report back after the next fill up.
 

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Yeah, I think that the check valve modification is best. I just did mine today, I had to drop the tank anyways. Kudos to you all that tackle that job without dropping the tank, I had a hard time getting the filler hose off of the tank, even though the tank was lowered a few inches.

I also had a heck of a time getting the check valve out of the tank. After I finally did, I looked at it real good. So, for of all you that still need to do this, it looks like if you turn it CCW, like you're trying to unscrew it, it looks like it will pop off easier.
 

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The GM fuel filler hose/flap valve is a band-aid that does not address the root cause.

The issue is caused by a sticking anti-rollover valve in the fuel tank. It manifests as either (1) fuel spit back when fueling caused by the valve being stuck open, (2) the gas pump continually clicking off because the valve is stuck closed or nearly closed resulting in it taking forever to fill the tank, or (3) both depending on where the valve is stuck on a particular day. The GM filler hose hack only addresses symptom #1.

The fix is to drop the tank, remove the anti-rollover valve and sand down the nubs on the plastic plunger a bit until it moves freely, then reinstall. No new parts are necessary and the repair is free if you DIY.

Some videos:

 

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Discussion Starter · #1,108 ·
I haven’t been following this thread much and I’m glad to see the improvised filler has helped people. That’s the first I’ve seen of how to pull out the check valve and fix the real problem - awesome!! That’s definitely on my short list to get done now.

When I came up with that filler hose fix it was meant to be temporary but it’s been working for me for over 5 years so far. It was born out of sheer anger toward Chrysler Corporation for not being willing to help out with a known problem. They gave JK tanks a lifetime warranty to get the NHTSA off their back and left those of us with 05-06 models up $#!t creek. They offered to give me a discount on a “new” tank which would’ve simply developed the same problem over time with exposure to ethanol blended gas.

I never knew before today that valve could pop out like that and you could sand it down to add clearance. Like I said...definitely gonna do that in the near future.

Thanks to everyone for all the input.
 

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Discussion Starter · #1,109 ·
Another to to consider is whether or not the GM hose performs the same safety function as the check valve. Besides preventing headaches at the gas pump, the check valve is supposed to prevent fuel leakage of you roll over.

I'm just asking. Does the GM hose prevent fuel leakage in a rollover?
No it does not, but where is the gas going to go if it gets in the filler neck but the cap is still sealed? Is the evap system fully sealed in case of a roll over? If this were something to be seriously concerned about I question whether there are other steps that should be taken also. I know what things are done to off road race cars in this regard. I was in a gas fed fire in a race car in Mexico (have the skin grafts to prove it) so I have personal experience with the potential for bad things, but I am comfortable with GM hose.
This is exactly the reason the hose was always meant to be temporary and why I'm psyched to finally learn about the valve fix. The valve in the hose only addresses the spillage at a gas pump. I don't plan on rolling over, but the fact that my valve has been stuck open for years has been bugging me for years and I've been reminded of it every time I gas up.
 

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This is exactly the reason the hose was always meant to be temporary and why I'm psyched to finally learn about the valve fix. The valve in the hose only addresses the spillage at a gas pump. I don't plan on rolling over, but the fact that my valve has been stuck open for years has been bugging me for years and I've been reminded of it every time I gas up.
If you jeep gets upside down you will have more fluid issues, including fuel, than this valve (whether in the tank or the hose) will solve.
 

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I swapped a '05 TJ fuel tank into my project JK pickup truck because the EVAP system is similar and pretty easy to plumb. I got my tank from a local salvage yard with unknown history

It absolutely would not take gas at a reasonable speed, only at a trickle.
I performed the envoy fuel flapper repair and it didn't help.
I dropped the tank and removed the factory ICV, it didn't help.
I unhooked the EVAP lines to be sure that my canister wasn't the issue and it still wouldn't accept gas.
I pulled the tank again, left the filler attached and tried to fill it.... Nothing
If I blow in the filler with my mouth, the tank builds pressure. Very slowly exhausts out the 5/8" EVAP line.
If I pull the fuel basket, gas flows into the tank perfectly. So I know the restriction isn't getting gas into the tank, it is getting the air out.

Reached inside and pulled the cap off the C/V valve along with the guts (a couple of plastic pistons and some light springs.) That also didn't help..... But after wrestling the tank around and getting aggressive I heard a click inside the C/V valve and now it is working correctly.

Apparently inside of the C/V there is a diverter that allows the EVAP line to flow air until the tank is full then it blocks the opening to kick the pump handle off. Not exactly sure how I got it free, not sure how long it will last. Figured it might help some of guys who can't get their TJ to take gas at all.
 

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Here is an explanation from my '05 FSM.

As fuel starts to flow through the fuel fill tube, it
opens the normally closed check valve and enters the
fuel tank. Vapor or air is expelled from the tank
through the control valve and on to the vapor canister.
Vapor is absorbed in the EVAP canister until
vapor flow in the lines stops. This stoppage occurs
following fuel shut-off, or by having the fuel level in
the tank rise high enough to close the control valve.
This control valve contains a float that rises to seal
the large diameter vent path to the EVAP canister.
At this point in the refueling process, fuel tank pressure
increases, the check valve closes (preventing liquid
fuel from spiting back at the operator), and fuel
then rises up the fuel filler tube to shut off the dispensing
nozzle.

The check valve mentioned in the last sentence is the one that may stick open which is the subject of this thread.

There have been others that have slow filling issues caused by a stuck closed check valve or non functioning vent so this post is good info.
 

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Control valve from the inside of the tank, you can see the cover that can be removed.

The float pistons and the springs that help them to float.

The inside of the C/V inside the tank. The floats fit very loose, unlikely to get hung.

The control valve has something else inside of it that I haven't figured out how to access. That something else is what was hung in my tank. It makes an audible click and has a huge effect on the flow in the EVAP line
 

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On my '06 Liberty, I had issues with fuel spitting back at me when filling at the pump. I dropped the tank, pulled out the backflow check valve in the fuel fill inlet and confirmed that the 3 friction points on the check valve were tight and causing the valve to stick OPEN. I sanded these 3 points down with sandpaper until the spring loaded valve traveled freely in its channel. Re-installed and fuel did not overflow tonight when I filled it up to the top.. YAY!

Some random notes on my process....

1. I Only disconnected 4 things off the tank.... the infill rubber tube with hose clamp, the fuel tank breather line (soft rubber line to a 'charcoal canister'? mounted to the underbody), the Main Fuel output line (once I figured out how to depress the button on it, it popped right off, putting it back was more difficult than taking it off) and the Electrical Connector (be sure to remember to disconnect your battery peeps!) on the fuel sending unit.
2. The thinner and more solid breather line on the left side of the tank that goes up year the fuel fill inlet, I just twisted it on it's connector so it went upwards as the tank dropped.
3. I was able to just get the tank on the ground and did not need to lift the jeep up higher to get access to what I needed.
4. I recommend cleaning off the top of your gas tank with water and towels so that when you remove the fuel sender unit clamp ring, that you don't get dirt in your tank.
5. Also take off the green o-ring gasket and clean it off, get the whole area clean before reaching into the tank.
6. I was pretty sure I was going to break off the internal check valve when I was trying to pop it off by bending it at the base, but eventually it did pop with rotating constant pressure. When it pops, if you keep your finger in the slots for the check valve, it won't fall into the tank... there are 3 parts, the plastic valve, the spring and the valve base (collar?). Make sure you have all 3. :)
7. Putting it back on was a mystery process... it seems to be keyed, but I wasn't really able to feel the keys... before you take it off, note the position of the two slots by feel... then put it back the same way. It requires some odd pressure with your arm and since I was under the back of the vehicle, maybe that is why it was not super easy, but I eventually got it on there and it felt like it had clicked in all the way.

The whole process took me about 2 hours after getting a U-joint to access the rear tank hanger bolts which on my Jeep were partially blocked by the Tow Hitch.

Good luck!
 

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You do understand that this thread is for TJ/LJ'S, right?

On my '06 Liberty, I had issues with fuel spitting back at me when filling at the pump. I dropped the tank, pulled out the backflow check valve in the fuel fill inlet and confirmed that the 3 friction points on the check valve were tight and causing the valve to stick OPEN. I sanded these 3 points down with sandpaper until the spring loaded valve traveled freely in its channel. Re-installed and fuel did not overflow tonight when I filled it up to the top.. YAY!

Some random notes on my process....

1. I Only disconnected 4 things off the tank.... the infill rubber tube with hose clamp, the fuel tank breather line (soft rubber line to a 'charcoal canister'? mounted to the underbody), the Main Fuel output line (once I figured out how to depress the button on it, it popped right off, putting it back was more difficult than taking it off) and the Electrical Connector (be sure to remember to disconnect your battery peeps!) on the fuel sending unit.
2. The thinner and more solid breather line on the left side of the tank that goes up year the fuel fill inlet, I just twisted it on it's connector so it went upwards as the tank dropped.
3. I was able to just get the tank on the ground and did not need to lift the jeep up higher to get access to what I needed.
4. I recommend cleaning off the top of your gas tank with water and towels so that when you remove the fuel sender unit clamp ring, that you don't get dirt in your tank.
5. Also take off the green o-ring gasket and clean it off, get the whole area clean before reaching into the tank.
6. I was pretty sure I was going to break off the internal check valve when I was trying to pop it off by bending it at the base, but eventually it did pop with rotating constant pressure. When it pops, if you keep your finger in the slots for the check valve, it won't fall into the tank... there are 3 parts, the plastic valve, the spring and the valve base (collar?). Make sure you have all 3. 🙂
7. Putting it back on was a mystery process... it seems to be keyed, but I wasn't really able to feel the keys... before you take it off, note the position of the two slots by feel... then put it back the same way. It requires some odd pressure with your arm and since I was under the back of the vehicle, maybe that is why it was not super easy, but I eventually got it on there and it felt like it had clicked in all the way.

The whole process took me about 2 hours after getting a U-joint to access the rear tank hanger bolts which on my Jeep were partially blocked by the Tow Hitch.

Good luck!
 

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Here's my
You can get this part new for around $30 with shipping or look up GM TSB: 04-06-04-003A for a list of vehicles to try and score one from a salvage yard.

[UPDATE: Adding this list because it's looking like we're depleting the NOS supply of these old hoses. Salvage yard hunting may have to start happening.]
2003 Chevrolet TrailBlazer with 83 L (22 Gallon) Fuel Tank (RPO NNK)
2003 GMC Envoy with 83 L (22 Gallon) Fuel Tank (RPO NNK)
2003 Oldsmobile Bravada with 83 L (22 Gallon) Fuel Tank (RPO NNK)
2002-2003 Chevrolet TrailBlazer EXT
2002-2003 GMC Envoy XL
2004 Buick Rainier
2004 Chevrolet TrailBlazer, TrailBlazer EXT
2004 GMC Envoy, Envoy XL, Envoy XUV
2004 Oldsmobile Bravada
Built Prior to December 2003

Fuel filler lower hose part #15131046:




The bulge in the middle is a little flapper valve:


Here's our lower hose that connects the filler tube to the tank:
I need to do this again - this time on my 06. Gm tsb 04-06-04-003a. Ok here goes


Sent from my iPhone using Tapatalk
 

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I need to do this again - this time on my 06. Gm tsb 04-06-04-003a. Ok here goes


Sent from my iPhone using Tapatalk
I need to do this again - this time on my 06. Gm tsb 04-06-04-003a. Ok here goes


Sent from my iPhone using Tapatalk
Better off dropping the tank and fixing the internal valve, it really is not too hard to do. I had done the GM hose and still occasionally had filling issues when the factory valve stuck closed. I had recently pulled the tank to move it back and decided to give it a shot, was surprised how easy it was. I will say popping the valve off almost feels like you are breaking it but once you have it out its a few minutes with some sandpaper and then wipe it clean and re-assemble.
 
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