Confused, empty tank of gas would only take 8 gallons

[Fast4esT]

Gas light was on, had driven 355 miles since last fill up. The gas pump was acting kinda funny and pausing every few seconds for a split second rather than smoothly pumping fuel and watching the dollar and gallons rise. It stopped at 8 gallons and everytime I tried to add more it would stop. I figured the pump had a problem so went in and paid and asked if it had an issue, they said nope.

Got in car and it says it's full of gas on the gauge. I only added 8 gallons, I had driven 350 miles and my light was on when I stopped for gas.

I don't understand what's going on.

[jubei4769]

bad gas level sender

[JEENYUS]

That seems odd. One time I was adding gas to the tank and it kept turning off like you described. I drove it for a little bit and then took it back to fill it up and it seemed to work. My guess is there's some sort of back pressure preventing it from filling up. The gas pump detects the pressure and shuts off. Do you have anything currently wrong with your car? PCV working fine? If you open the gas hole do you feel air being sucked in or blown out?

[vjborelli]

Clogged vent tubes, or charcoal canister. Were you filling it with the car running, or off? When the engine is off, the gas tank is vented through the charcoal canister to the leak detection pump. When the car is running, the gas tank is vented to the intake via the N80 purge valve.

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[Fast4esT]

Car was off, no I did not hear or feel any air. Usually when I open the gas cap I get a bit of pressure release sound but don't recall it this time. My pcv system is deleted right now, been thatvway since I got the car. First time this has happened.
What is the transfer pump?

Is the charcoal canister inside the rear driver wheel well or up front? My driver side fender liner is pretty shot, I thought there was something fueling oriented in there that's not supposed to get wet.

I don't think the gauge sender would stop fuel from going in the car would it?

[vjborelli]

You shouldn't be getting any pressure release sound when you open your gas cap.

The charcoal canister is mounted under the car behind a panel under the spare tire well. The leak detection pump is located on the driver's side of the car (left hand drive), in rear wheel well behind the wheel liner. The N80 (AKA: EVAP purge valve) is located at the top of the air box in the engine bay.

The N80 valve is a normally closed valve, and opens via the ECU to vent gas vapors to the turbo inlet hose when the engine is in boost, and to the intake manifold when the engine is under vacuum (idle or light load).

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[Fast4esT]

If a charcoal canister is clogged can it be cleaned?

[jubei4769]

If a charcoal canister is clogged can it be cleaned?

not sure but there was a good thread here on the forums about that issue

[texasboy21]

Check your N80 - it should click - above your airbox.

[vjborelli]

If a charcoal canister is clogged can it be cleaned?

No, but it can technically be bypassed. I know there was a DIY for it floating around on the forum.

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[Fast4esT]

I pulled a hose from the LDP and was able to blow through it, assuming that the pump is good. I also disconnected the hose to the carbon canister and blew lightly with compressed air, had gas cap off at the other end and fuel flap open, could feel the air coming through. Assuming the evap a buster is not clogged. The n80 purge valve is not connected to anything but electronics.

One thought is maybe there was a problem at the pump and it think and charged me for 8 gallons when really I got an actual full tank. Just an idea, in the mean time gonna drive around and try to add gas again soon. See how the gauge behaves.

Still swimming for ideas here
Thanks all

[vjborelli]

I pulled a hose from the LDP and was able to blow through it, assuming that the pump is good. I also disconnected the hose to the carbon canister and blew lightly with compressed air, had gas cap off at the other end and fuel flap open, could feel the air coming through. Assuming the evap a buster is not clogged. The n80 purge valve is not connected to anything but electronics.

One thought is maybe there was a problem at the pump and it think and charged me for 8 gallons when really I got an actual full tank. Just an idea, in the mean time gonna drive around and try to add gas again soon. See how the gauge behaves.

Still swimming for ideas here
Thanks all

There is also a vent tube that runs from the tank up to the filler neck that the pump uses to identify when the tank is full.

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[Fast4esT]

how do you access that tube from the tank to the filler neck?

[johnnyblaze26]

Did you get this figured out? I started my car for the first time in like 6 weeks today and the gas needle didn't move. I was pretty sure there was a good deal of gas in there, but I drove to the gas station to be sure. It took about 8 gallons before the pump said it was full. Started the car back up and now the needle said it was only 1/4 full. I drove it around for a bit and the needle slowly crept it's way up to full (took about 20 minutes). Not sure if there was a pressure issue there from it sitting so long or what, kind of a weird issue.

[Myst420]

It sounds like the float portion of your sending unit got stuck. It may work itself loose after driving around a bit. If not, I think the only way to replace it is by replacing the fuel pump,

[Fast4esT]

I've driven 250 miles so far and my needle is between 1/4 and 1/2 tank as usual for this mileage. I'm guessing the pump was not calibrated as everything on the car seems to be functioning correctly. Figured if I only had 9 gallons of gas I'd be running out about now

[n7plus1]

you may want to just replace the n80 while youre at it. could be failing and causes other issues as you pack on the miles.