Novak Conversions Jeep Wrangler TJ engine mounts

Magic Gas Tank (Not Your Average Slow Filling Thread!)

WarWobble

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I wanted a title that would communicate the unique nature of my refuling issue to avoid being linked to that same tired old thread about 05 & 06 TJs and their splashback valves (with the video of the mechanic who looks right at a TJ and calls it a Cherokee).

At the moment, my biggest regret in life is the bone-headed decision to replace a gas tank skid plate that was so rusted apart that it was in multiple pieces strapped together with structural zip-ties. Clearly I should've just slapped another zip-tie on there!

Ever since I replaced the skid plate, straps, filler-neck, filter, and sender seal, my 4.0L 03 TJ has been been in full rebellion at the gas station. It takes great patience and skill to pull the pump's trigger lightly enough to not shut the pump off immediately, making refueling into a long and humiliating ordeal.

No, my splash-back valve does not look like that, it was not stuck, and I went back and ripped it out anyways just in case.

No, no lines were pinched above the tank. How would that happen anyway? They're all hard plastic except for the one 7” rubber line to the neck.

First, I tried replacing the filler hose, since it looked pretty kinky (would not take home to mother). No change.

Some basic troubleshooting logic from Identifix made sense to me:

Disconnect lines from the tank to the EVAP system and the vent line to the neck. If the issue persists, the problem is in the tank.

With the EVAP system completely disconnected from the tank and filler neck, there was no change. It would seem that the EVAP system is exonerated and the problem in the tank.

Since I do not care if my EVAP system throws codes, I dropped the tank again and gutted any non-essential components that could possibly become stuck and interfere with fuel flow or venting. I removed the splash-back valve from the filler inlet, and removed the two check valves from the two vent outlets on top of the tank. Aside from the sender/pump assembly, my fuel tank no longer has any moving parts that could possibly bind.

To my horror, the problem still persisted at multiple gas stations and it made no difference whether the EVAP and filler vent lines were disconnected.

What could prevent a tank that can vent freely to the atmosphere from accepting fuel though a new and unrestricted filler hose?

The filler neck? Isn't that just a tapered tube with a flap? The flap appears to work and the tube appears unrestricted. There is a very slight angle where the filler neck meets the filler tube, but it almost seems crazy to think it would have any effect on the flow of fuel.

I'm out of sane ideas and would be happy to read any suggestions of any sanity level.
 
I wanted a title that would communicate the unique nature of my refuling issue to avoid being linked to that same tired old thread about 05 & 06 TJs and their splashback valves (with the video of the mechanic who looks right at a TJ and calls it a Cherokee).

At the moment, my biggest regret in life is the bone-headed decision to replace a gas tank skid plate that was so rusted apart that it was in multiple pieces strapped together with structural zip-ties. Clearly I should've just slapped another zip-tie on there!

Ever since I replaced the skid plate, straps, filler-neck, filter, and sender seal, my 4.0L 03 TJ has been been in full rebellion at the gas station. It takes great patience and skill to pull the pump's trigger lightly enough to not shut the pump off immediately, making refueling into a long and humiliating ordeal.

No, my splash-back valve does not look like that, it was not stuck, and I went back and ripped it out anyways just in case.

No, no lines were pinched above the tank. How would that happen anyway? They're all hard plastic except for the one 7” rubber line to the neck.

First, I tried replacing the filler hose, since it looked pretty kinky (would not take home to mother). No change.

Some basic troubleshooting logic from Identifix made sense to me:

Disconnect lines from the tank to the EVAP system and the vent line to the neck. If the issue persists, the problem is in the tank.

With the EVAP system completely disconnected from the tank and filler neck, there was no change. It would seem that the EVAP system is exonerated and the problem in the tank.

Since I do not care if my EVAP system throws codes, I dropped the tank again and gutted any non-essential components that could possibly become stuck and interfere with fuel flow or venting. I removed the splash-back valve from the filler inlet, and removed the two check valves from the two vent outlets on top of the tank. Aside from the sender/pump assembly, my fuel tank no longer has any moving parts that could possibly bind.

To my horror, the problem still persisted at multiple gas stations and it made no difference whether the EVAP and filler vent lines were disconnected.

What could prevent a tank that can vent freely to the atmosphere from accepting fuel though a new and unrestricted filler hose?

The filler neck? Isn't that just a tapered tube with a flap? The flap appears to work and the tube appears unrestricted. There is a very slight angle where the filler neck meets the filler tube, but it almost seems crazy to think it would have any effect on the flow of fuel.

I'm out of sane ideas and would be happy to read any suggestions of any sanity level.
The filler neck is vented. Vent sounds clogged.
 
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Based on what Blaine said:
Problem here somewhere?
1725477519214.jpeg


Pull it out and verify that vent tube is open?
 
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Would disconnecting the vent hose to the filler neck also verify whether the filler neck vent tube is to blame? Because that has been tried.
 
Would disconnecting the vent hose to the filler neck also verify whether the filler neck vent tube is to blame? Because that has been tried.

No,you just verified that the hose isn't the problem. Not the filler neck vent tube or filler itself. Is it aftermarket?
 
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No,you just verified that the hose isn't the problem. Not the filler neck vent tube or filler itself. Is it aftermarket?

It is a TRQ aftermarket filler neck... I guess there could just be something off about how it's manufactured that pump nozzles hate. I can push an inspection camera in one end and out the other. Maybe I'll try to get a used MOPAR unit off eBay.
 
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It is a TRQ aftermarket filler neck... I guess there could just be something off about how it's manufactured that pump nozzles hate. I can push an inspection camera in one end and out the other. Maybe I'll try to get a used MOPAR unit off eBay.
Trusted Reliable Quality (TRQ) parts sometimes aren't. I'd listen to mrblaine's advice and take it first.
 
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I went ahead and ordered eBay’s cleanest and finest used MOPAR filler neck in the hope that TRQ subtly bungled something about the design of the area where the nozzle rests. If it arrives by Saturday, I can put it in this weekend. If it works, that TRQ is getting one hell of a negative Amazon review!
 
The flap appears to work and the tube appears unrestricted

What flap? My 05 filler tube has no flap. Some added a GM flapper thing as a non-solution to the sticking check valve. Is your filler hose OEM?

Could the flapper be installed backwards?
 
What flap? My 05 filler tube has no flap. Some added a GM flapper thing as a non-solution to the sticking check valve. Is your filler hose OEM?

Could the flapper be installed backwards?

The filler neck has a flap that is pushed out of the way by the nozzle. The filler neck is made by TRQ, and I'm about to try replacing it with a used MOPAR filler neck. The filler hose has no flap. Nobody has replaced it with the GM hose.
 
The filler neck is vented. Vent sounds clogged.

Would disconnecting the vent hose to the filler neck also verify whether the filler neck vent tube is to blame? Because that has been tried.

It has to vent. If you haven't verified that it can do that from inside the tank to atmosphere via all pathways, then you don't know.

I went ahead and ordered eBay’s cleanest and finest used MOPAR filler neck in the hope that TRQ subtly bungled something about the design of the area where the nozzle rests. If it arrives by Saturday, I can put it in this weekend. If it works, that TRQ is getting one hell of a negative Amazon review!

Did you do what @mrblaine suggested before you ordered parts to throw at the problem?
 
Did you do what @mrblaine suggested before you ordered parts to throw at the problem?

No. Since the filler neck is the only proposed problem so far, it doesn't matter to me whether I'd be replacing it because of a defect in the vent tube or a defect in the filler opening. If I blew compressed air though the vent tube part, I'd still be suspecious of the other part of the part. The only reasonable way to eliminate the filler opening as a suspect is with another filler neck (I belive the rusty original has been collected for scrap by now). I'm not adventurous enough to remove the filler neck and try pumping gas directly down the soft tube.
 
No. Since the filler neck is the only proposed problem so far, it doesn't matter to me whether I'd be replacing it because of a defect in the vent tube or a defect in the filler opening. If I blew compressed air though the vent tube part, I'd still be suspecious of the other part of the part. The only reasonable way to eliminate the filler opening as a suspect is with another filler neck (I belive the rusty original has been collected for scrap by now). I'm not adventurous enough to remove the filler neck and try pumping gas directly down the soft tube.

FYI the other part is just an open tube. Not much can go wrong with it.
 
FYI the other part is just an open tube. Not much can go wrong with it.

That was exactly my thinking at the time of the original post, but since then, desperation has made me more open-minded to all kinds of possibilities. What if there is some defect or obstruction that is splashing fuel back into the nozzle's venturi opening?
 
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Buena suerte señor.

¡Gracias!

Since next weekend is the next time I will be in a position to do any work to the Jeep, of course I will blow some compressed air through the vent tube to satisfy our curiosity at that time.

Because the TRQ filler neck is new and symptoms started at the time of installation, whatever blockage that may be in the tube will have come from the factory. This would make it less likely to be something that can be easily unclogged like mud or cocoons, and more likely to be something difficult to remove, such as a glob of exess metal or paint.

I am glad I have a facory filler neck on the way, because it gives me hope for a resolution this weekend to a very annoying problem on my daily driver, despite cultural taboos about ordering parts prior to 100% certainty of diagnosis.
 
Novak Conversions Jeep Wrangler TJ engine mounts