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Discussion Starter #1
A few weeks ago I couldn't fill up my XG350 tank with gas. The nozzle kept clicking off as if it was full, but it wasn't. I've read a slew of threads on various sites about this problem. It seemed to me that even Hyundai dealers had problems with solving this, so I decided to venture on my own. It is crucial that you get a diagram of the EVAP system for your vehicle. This diagram is available on the Hyundai site hmaservice.com. Anyway, to troubleshoot you need to remove the plastic cover in the wheel-well on the rear drivers side. After removal you will see all the lines in the EVAP system. The charcoal canister is sortof behind the wheel, strapped up there, a little smaller than a shoebox.

Anyway, there are really only a few possible causes for this. Gas can't get in because
- the filler neck has a valve when it gets to the tank, so it could be obstructed there, going in
- the air cannot vent out of the tank when you are filling it (i believe this is more common)

The air from the tank vents from a Fuel valve that connects to a 4-way valve, then through some tubes, then through the charcoal canister, then to outside air (look at the EVAP diagram). Many threads suggest an obstruction at the charcoal canister. To check this, just disconnect the 1/2 inch hose before the canister, if you still can't fill it, the obstruction is not there. So I ended up disconnecting the hose all the way back to the Fuel value and still couldn't fill it, thus I assumed it was Fuel Vent valve, a $45 part. But you can't get to this part without dropping the tank, and the exhaust system is in the way and would need to be removed. Ok, this is not as crazy as it sounds, but I drilled a 3 inch hole in the trunk floor right above this part to gain access, using a hole saw that cuts metal (it connects to your drill). If you lift the carpet in your trunk, you will see an access panel in the center rear that allows access to the fuel pump. The fill vent value is to the left of that. 3 screws hold it in and its about 5-6 inches long with a 1/2 hose connected to it. Anyway, I swapped it, connected it back up, and BAM I can put gas in my tank again.

If anyone would like more information about this, send me a message.

Mike
 

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So... are you saying that you couldn't get to the fill vent through the trunk access panel? So you had to cut a 3 inch hole 5 or so inches to the left of it?
And you say the problem in your case was definitely the valve, right?
 

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QUOTE (mpmiller37 @ May 16 2011, 10:48 AM) index.php?act=findpost&pid=446217
A few weeks ago I couldn't fill up my XG350 tank with gas. The nozzle kept clicking off as if it was full, but it wasn't. I've read a slew of threads on various sites about this problem. It seemed to me that even Hyundai dealers had problems with solving this, so I decided to venture on my own. It is crucial that you get a diagram of the EVAP system for your vehicle. This diagram is available on the Hyundai site hmaservice.com. Anyway, to troubleshoot you need to remove the plastic cover in the wheel-well on the rear drivers side. After removal you will see all the lines in the EVAP system. The charcoal canister is sortof behind the wheel, strapped up there, a little smaller than a shoebox.

Anyway, there are really only a few possible causes for this. Gas can't get in because
- the filler neck has a valve when it gets to the tank, so it could be obstructed there, going in
- the air cannot vent out of the tank when you are filling it (i believe this is more common)

The air from the tank vents from a Fuel valve that connects to a 4-way valve, then through some tubes, then through the charcoal canister, then to outside air (look at the EVAP diagram). Many threads suggest an obstruction at the charcoal canister. To check this, just disconnect the 1/2 inch hose before the canister, if you still can't fill it, the obstruction is not there. So I ended up disconnecting the hose all the way back to the Fuel value and still couldn't fill it, thus I assumed it was Fuel Vent valve, a $45 part. But you can't get to this part without dropping the tank, and the exhaust system is in the way and would need to be removed. Ok, this is not as crazy as it sounds, but I drilled a 3 inch hole in the trunk floor right above this part to gain access, using a hole saw that cuts metal (it connects to your drill). If you lift the carpet in your trunk, you will see an access panel in the center rear that allows access to the fuel pump. The fill vent value is to the left of that. 3 screws hold it in and its about 5-6 inches long with a 1/2 hose connected to it. Anyway, I swapped it, connected it back up, and BAM I can put gas in my tank again.

If anyone would like more information about this, send me a message.

Mike
This also happened to my XG350. I took the rear wheel off on fuel filler door side. There is a canister with charcoal beads under the wheel well. use compressed air and blow all of the beads out. What happens is, when you overfill the tank, gas enters this canister and causes the beads to swell. After doing this it will take gas properly.
 

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Discussion Starter #4
Problems again ...

After a year or so this problem started reocurring and I've been dealing with it off and on for the past year. I disconnected the lines all the way back to the tank vent again and still can't fill it up. Leaves me to believe that the fuel vent valve on the tank is bad again, but that seems pretty strange. The only other possibility is some obstruction on the input side. I'm going to unscrew the fuel vent valve at the gas station and try to fill it up. Will update soon.
 

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Hyundai XG350 Fueling Problem

I had the same problem and just fixed it by replacing both the Fill Vent Valve ($50 at dealer) and the Charcoal Canister ($196 on eBay). The problem is that the charcoal in the fuel vapor canister breaks up and escapes into the supply hose, working its way to the Fill Vent Valve, which then blocks the vent closed. Someone else on another site reported finding charcoal bits in their Fill Vent Valve when they replaced it. I thought they were nuts because after viewing the EVAP system diagram at hmaservice.com (thanks for the tip, npmiller37), I figured there is no way that charcoal bits could work their way against the normal directional vapor flow, proceed up and down the Liquid-Vapor Separator and get to the Fill Vent Valve. But when I removed my Fill Vent Valve, guess what fell out? Bits of charcoal! From what I understand overfilling the gas tank, for which I was always guilty, causes liquid gas to enter the charcoal canister, which breaks up the compacted charcoal. I dropped my canister and charcoal practically poured out.

Here is the step-by-step procedure I followed:

First I removed the charcoal canister. You do not need to remove the left rear tire or the plastic wheel well cover, or even jack up the car. I simply laid on the ground behind the left rear tire and removed the canister support bracket - 1 screw. Then I removed the canister's protective holder/cover, which is held on with a large cable tie. Next I disconnected all the hoses and the attached Purge Control Solenoid Valve (I actually replaced that too for the heck of it in case it had charcoal lodged inside. $30 on eBay) All the hose connections use simple compression clamps, so use a pair of pliers to slip off the clamps, and a screwdriver to pry the hoses off the nipples. Shake charcoal from the hoses. Don't install the new canister just yet.

Then using npmiller37's suggestion, I accessed the Fill Vent Valve from the trunk. I first popped off the plastic cover over the fuel pump and moved the pump's electrical cord out of the way. From the opening I saw a valve about 3 inches to the left of that opening. Using a 3 1/4 inch hole saw ($20 at Lowes), I cut out a hole above that valve... and then figured out that this was actually the Fuel Cut Valve. But from the hole I cut I could now see the Fill Vent Valve just left of the Fuel Cut Valve, so I cut another hole slightly overlapping the first hole I cut. (Note to Hyundai - why would you build in an access panel to the fuel pump but not the Fuel Cut and Fill Vent Valves? Duh!) (Note to hole cutters - Cutting a hole in metal spews metal shavings everywhere. Best to have a shop vac handy. I cut down the mess by fashioning a plastic shroud cut from a 5-gallon bucket, so that as I drilled, most of the shavings were contained within the shroud. I also removed the backrest and bottom seat for convenience and easier vaccuuming, but it is not necessary to do so.) Three simple screws hold the Fill Vent Valve in place. First two screws loosened easily. Third screw wouldn't come out with 6 doses of Lock-Ease overnight and an impact driver! Finally drilled it out with a screw extractor (after another trip to Lowes) I had another 10-20 machine screw, and cut it to 1/2 inch length to replace the screw I drilled out, saving another trip to the hardware store. Before removing the hose from the valve, I tied a wire to the hose to make sure I could retrieve it if it slipped down out of reach. Disconnected the hose, lifted out the valve, and shook the charcoal bits out of it in disbelief. Next I blew compressed air into the hose to clear it of charcoal bits to prevent recurrence of the problem. Maybe one or two dozen bits of charcoal came out the canister end... more than enough to clog up the new valve if they had been left in the hose. Before installing the new charcoal canister, I went to the gas station and pumped gas to prove the new Fill Vent Valve was working. While pumping gas, I put my hand behind the left rear tire and I could feel the cool air escaping from the Fill Vent Valve hose... success!

Back home, installed the new canister and purge valve and hooked up the hoses... again simply done just by laying on the ground behind the tire. Secured the canister bracket. Done under the car.

Then all that was left was repairing the holes in the trunk. I am actually glad that I cut one extra hole in error, as now I have access to both valves if ever needed. I was just going to screw a piece of sheet metal over the holes, but decided on a more flush and weatherproof solution. I put two strips of gorilla tape along the length of the two holes from underneath... sticky side facing up (I cleaned the metal underneath first). Then I laid the hole cutouts back in place, and they were securely held by the gorilla tape. Then I caulked around the edges of the cutouts with silicone caulk to hold everything in place and provide an extra weatherproof measure. When the caulk cured, I placed three strips of gorilla tape across the top of everything for a uniform cover, then taped the electrical cord for the fuel pump back in place. Done in the trunk. Done with the car. Done with taking 20 minutes to fill up my gas tank!

Never again will I overfill my gas tank. When the fuel pump shuts off, no more topping it off!

We can all thank the EPA for this higgledy-piggledy mishmash of crap in our cars.
 
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