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Inner Flap in Fuel Filler

The spring loaded flap in the fuel filler neck of my 2003 Tundra has gone missing. I’m almost certain there was a flap there, but now it is gone. Is it possible for it fall into the tank? Will it hurt anything if it did. Will it hurt anything to not have it in place? What the heck is it for anyway?

The flap is called a “rollover valve”. It supposedly keeps gas from flowing out during a rollover. I don’t think it can do any harm because the fuel pump inlet is protected by a “sock” that acts as a filter of sorts. That valve is missing in a lot of vehicles so…join the club.

Thanks for that. I was worried that it might block the punp or block the filler tube. I was considering trying to pull the rubber section between the tank and the filler hole to see if it was in it.

The flap, at the TOP of the fuel filler tube, is NOT the roll-over (or, check) valve. THAT valve is at the base of the filler tube. The flapper, at the top of the filler tube could fall and jam the check valve. If this happened, it could cause an EVAP DTC code to set and the check engine light to come on. Have light?

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No light, but I haven’t driven the truck since I noticed the missing flapper. (I had emptied a Blitz can into the truck with gas left over from my generator supply.) It was when I was ready to empty a second can in that I noticed the flap missing.

I took the “rubber” filler hose lose. It runs from the nozzle inlet over the frame rail and to the inlet pipe on the tank. The flap was not in the filler hose. Nor could I feel it as far as my finger could reach into the tank pipe.

If the flap is in the truck, it is in the tank. I searched the area around the truck to see if it hung on the blitz tank’s filler tube, but found nothing. I have a hard time believing those flappers could fall through the metal part of the piping. I think it would be like a manhole cover. They supposedly can’t fall through the manhole. But the gods of mechanical misfortune are cruel indeed.

I guess my best option is to drive it and take my next action based on what happens. I don’t what else to do short of the things I’d do if there is problem.

Thanks for your response.

The true purpose of that little “flapper” is uncertain. Perhaps to keep liquid gasoline from blowing out of a pressurized tank on a hot day? Who knows…But if it drops down into the tank, it’s not a problem. The fuel-pump pick-up is protected by a fiberglass sock…

Thanks. My concern is that it will jam something. The only something that came to mind at first was the fuel pump. The prior post mentioned the check valve at the inlet to the tank. I hadn’t thought about it, but it sounds plausible.

I just really don’t want to go to the expense of fixing it if it isn’t problematic; just hope any failure isn’t disabling at a bad time.

The flapper in the filler neck is left over from the 70s. The first efforts at emissions controls included unleaded gasoline and catalytic converters. Leaded gasoline was sold for older models for many years at a cheaper price and higher octane than the unleaded. To prevent “unleaded” vehicles from being filled with leaded fuel it was mandated that the manufacturers install a restricted filler on the cars and fuel nozzles were required to be reduced in size to match. The spring loaded flapper was part of the restricting filler system.

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Thanks. There was a kid in my graduating class (about the time unleaded was introduced) who never bought gas; he’d siphon it. It was said he could tell the difference between leaded and unleaded by the tastes. His signature line was, “Eww! Unleaded!”

This is exactly what happened to my jeep. How expensive is it to get this fixed? I need the check engine light off.

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I doubt that the loss of a fuel fill restrictor flap is the cause of the check engine light to illuminate. What is the year and model of your Jeep and what fault code is causing the check engine to illuminate?

It’s a 2006 Jeep Liberty Sport. Advance Auto Parts said the code was something like “light evap leak”. I just bought this Jeep, and when I go to fill up the gas, I can’t walk away, because it never detects it’s full, and then it overflows. When I looked inside, it’s missing that little metal flap. So when I read this comment, I thought this must be what’s happening.

I don’t know if your fuel fill tube ever had a flap but it is not the cause of the leak, the fuel cap seals off the fill tube.

There is a fill control valve in the top of the fuel tank that blocks the vapor venting when the tank is full, this causes fuel to be driven up the secondary tube, splash across the fill nozzle and shut off the pump. The fuel fill control valve may be stuck.

The fault that you have may be due to a vapor leak in the fuel system. First inspect the vapor lines from the tank to the vapor canister and to the engine for split hoses at the ends.

Thank you for the advice! I don’t know how to work on cars, so I’ll have to bring it to a mechanic.

My 2010 Sonata is doing exactly that!

There are many failures that can cause an evaporative emissions system fault, it wouldn’t be caused by the fuel filler tube flap, those were replaced by fill tube check valves 20 years ago.

I’m inclined to disagree, because my little flap has recently gone missing, followed by check engine light with evap code, and suddenly I have an issue with my car randomishly losing power… The engine actually died today as I was making a u-turn. It’s got all the signs and symptoms of a fuel delivery issue, and it’s too much of a coincidence that the cursed little flap went AWOL right before these problems started. So… Now what? Without even looking at the car or telling me if these issues are related, and listening only to the “flap missing” part of my dilemma, the mechanics I’ve seen for it say they’ll have to replace the whole thing leading to the tank. I’m not very knowledgeable when it comes to the fill-up system, but that seems extreme and likely to come with a pricetag significantly higher than that spring loaded bit of tin is worth. Any recommendations?

If you believe that the fill tube flap falling into the tank is causing a fuel delivery problem like a failing fuel pump them simply replacing the fill tube will not solve the problem. If you have a vehicle old enough to have had that flap it is likely that something else is failing.