Gas pump always stops around 11 or 12 gallons

It has done this the last four times that I've filled up, and I have specifically used four different pumps, just to make sure it wasn't a pump issue. For some reason, when I am refilling an empty tank, it always stops around 3/4 full. Then I have to keep topping off for another 3-4 gallons until it's full. Any ideas what is causing this? - Anthony

Yah yah I'm not leaving till he gets a good answer. Mine is pulling the same trick where it wont read full when I know its topped off since it keeps kicking the fuel nozzle off. Even by FAA regs many things like a fuel gauge is only required to register there is fuel. Meaning accuracy is not important. I was told for the 996 the gauge should recalibrate after filling the tank. Some place I read that when disconnecting the battery and reconnecting the gauge might read wrong if the tank wasn't near full. I have been tempted but still haven't disconnected the battery and reconnected after filling up the tank in the hope that the gauge will consider the fuel level present as what should be read as full. Some time later when I drag some tools along with me I'll try that trick.

I had this happen at a Shell gas station about 3 weeks ago. I didn't realize it wasn't full until I drove away. The next time I got gas it was at a Chevron station and it filled right up. Last week I went to a different Shell station and it happened again. I'm wondering if certain pumps used by different stations or companies are just too sensitive. You mentioned that you tried different pumps but were they at different stations or different company's stations? Just wondering.

I'm not sure about the 996 but some cars and even military vehicles have a tube from the tank to the top of the filler neck that when the tank is nearly full it spits fuel into the filler neck where the nozzle is. With the unleaded style of hinged cap its hard to tell whats in there. I've given up nursing the last bit into the car figuring I'm just filling up the filler neck to do so. Which I don't feel is a good idea if I am doing it.

Angle of the pipe? My Wife's audi is very temperamental if the pump is pointing a certain way. So much that you need to only half "squeeze" the trigger? I just figured the bowser was pumping faster?

This happens with my car quite a bit as well. I know Andy (AudiOn19s) had a similar issue, but he could only pump cents at a time and I believe he said it had something to do with an evap line working loose after a spin at the track. Not sure if the two are related (I haven't tracked my car).

I've been told if you angle the pump handle upside down, it will take care of the issue. Its the way that I fill up my tank and I've never had the issue. Another thing I've been told is that due to the tank design, you shouldn't let the it go down below 1/4 full.

This one has been pretty heavily discussed. It could be a number of things. First, check fuse E6. If this fuse is blown, then the return flap in the tank isn't opening. At least that's the way I understand it. I've also heard that this is an issue if you let your tank get very low before you refill because of the way the 996 tank is designed. Finally, it seems to be gas station specific for me. BP stations always give me this problem. Marathon stations seem to never cause it. I think the type of pump matters.

What's the issue with letting your tank get low? How low is too low? I usually try to start an autocross with 1/4 tank; I'm often below 1/8 tank before we leave. I've never had an issue with fuel starvation in the corners or anything. This is the first I've heard of any issues with it.

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When you end up walking, you've run the tank too low.

it has been discussed and there is some piece in the tank (sorry I didnt follow the threads) that gets dirty/clogged/worn and can be replaced. BUT replacement of an item inside of the gas tank is seriously dangerous and although a couple people have done it, its best left to the pros Question... are the keys in the ignition? try removing them next time.....I dont think this had any effect, but was a "maybe" in a couple cases 2 links Link 1 Link 2

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Interesting. I tend to let the car get really low on gas before I fill up. On this last tank it was so low the miles till empty counter stopped showing any miles, and that was about 15 miles before I filled up! However, it never did this until the past two months, so I figured it had something to do with the cold weather and fuel expansion/pressure inside the tank.

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Check the E6 fuse, controls an emmission valve.

BMW,Lexus,Porsche and Mercedes dealers at different times have said do not use BP.

BP = British Petrolium... of course German cars dont like it

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The issue with letting the gas level get real low is the fuel pump is immersed in the fuel and is cooled by the fuel. A real low fuel level means there is little fuel left to absorb the heat from the pump. The pump runs hotter. A few instances is not sufficient to cause any problems but consistently running around with a low fuel level can over time degrade the fuel pump. Next with a tank with low fuel there is more sloshing. If there are any contaminants in the fuel -- water mainly -- this agitates the water off of the bottom of the tank where it normall resides and mixes it in the fuel. If this fuel with water gets ingested by the fuel pump it can block the fuel filter (had a truck engine stop like a switch was thrown once when I went around a sharp corner with a low fuel tank and upon inspection found a few drops of water in the inline fuel filter which acted to completely block fuel flow until I removed filter and blew out the water). If it makes it past the fuel filter the water can result in damage to the the injectors and then of course trigger a CEL from a misfire though this will be shortlived. I would hope the newer Porsches with direct injection systems have fitted a real good water trap to prevent any water from making it past the the 1st fuel pump into the high pressure fuel pump. If not or if it is being overwhelmed and people are driving these cars on a real low fuel tank this might account for some of the fuel pump failures these cars are experiencing. I remember from my time with my diesel powered car high pressure fuel pumps -- be they pumping diesel fuel or gas -- do not like water at all. And the fuel pump on the diesel was a very expensive item. The fuel filter -- just before the pump -- was huge and had a big water trap too. And when I drained it once in a while I always got a few drops of water out of it. So the water does make it up as far as the engine compartment. When automakers went with in-tank fuel pumps I stopped running gas tank real low except on rare occasions. I generally fill the gas tank when level showing 1/4 tank though I do once in a great while continue to drive to the point the low fuel light comes on. Most fuel -- just recently too -- I ever put into my Boxster's 16.9 gallon fuel tank was 15.23 gallons. Generally the fill up ranges from 10 gallons to 12 gallons sometimes getting into the 13 gallon figure. I know -- from my Auto-Xing days -- everyone likes to run low fuel level for the weight savings. Gas weights approx. 7.5 pounds per gallon and a few more gallons of gas is not going to cost you a trophy and might save you some trouble later down the road. Sincerely, Macster.

My car too doesn't play well with most gas nozzles. The upside down technique allows it to work, but so does holding it horizontal. I noticed that some stations now have signs saying not to hold the nozzle upside down and so, to avoid being yelled at, I tried horizontal and it worked.

It's touch and go for me. My issue is the same as the thread's author (adg). It's not that it's filled up full and the tank reads 3/4 like Pac's. So let's not get that confused. It should almost be a separate post. I do better with the basic nozzles with no fancy gas fume breather contraption at the end of the nozzle. The kind where you push in so the mouth of the contraption can cover the gas tube on car. The straight nozzle style typically fill up till full. It's an annoyance that just shouldn't be there in the first place (go Porsche). I don't buy the whole fill up at 1/4 else claim. The manual says nothing about this. I'll check the fuse.

There was some discussion on this topic a year or two ago. Consensus then was an issue with the filling tube on the 996, and its feedback loop (pressure relief). I understand that these things are not cheap to fix--may require the tank to come out. I just don't buy the tank 1/4 full theory.

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Hmm, I thought i saw something about an inaccurate gauge, didn't register fully the first time... So trying not to hijack the thread and maybe help someone out I'll try be brief. The aforementioned audi previously had an issue where the gauge would read half even when full. Solution was: Pull the fuel pump and instrument cluster fuse's Switch the ignition on (without starting the car). Turn off, replace fuse's and start the car. The gauge then reset itself. Not a porsche but possibly worth a try?

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Sounds like something fun to try. I'm pretty sure its a full tank when when its reading below full.

It's the gas pumps that cause it not to fill completely. I know for sure that Shell pumps do it. I have a gas card for Shell so I have to put gas from Shell and I noticed that it does there. I have had to put gas at other stations, and it did completely fill. What I do is pay attention to how many gallons it should have, then if the pump stops early, I usually top off once or twice, this usually fills it up all the way for me.

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This is what I have resorted to doing as well.

It's easy to get a spill that way though. When it's full, topping it off is bad.

Mine never fills up at shell. When I use the upside down method, I seem to get more fuel in the car. It' never quite gets up to the full line regardless of the pumps. Even when I use the upside down, it barely get's there or is just under the full line. I've never tried topping off as I don't want to have a spill. My average fill up from when the light comes on is around 13.6. Sometimes I'll get as much as 14 gallons in. Both my first and second 996 do the exact same thing. I figured it's normal.

<waving hands in the air> are you filling with the key in the ignition? I just wanted to know........

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Yes.

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No. Key is removed.

So I filled mine with the car running a few times and had some issues with the guage and with filling... I then switched to removing the key and either my car fixed itself, or it actually had some effect... I have not had guage issues or filling since???? I run it full to very low ever time too (seldom till the light comes on, but close) just a thought...... dont know why it would make a diff...

key has nothing to do with it by my experience. it's the pump style. the more sophisticated it is the more likely it won't top off full. it's tougher nowadays to get the simpler nozzles due to the emissions regulations at the pump level. not that i've ever used arco gas, but those pumps are the worst for the 911. the ones where you have to press in and have it catch before it dumps fuel.

I found Chevron in my area to have some of the old style pumps w/o that extra snout thing

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luckyyy

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Me too there's a Chevron aroound the corner from where I live.

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My Turbo owners manual cautions against hard cornering with the low fuel level light on. Running gas tank level real low with submerged fuel pumps has been a problem for as long as fuel pumps moved from outside the tank to inside the tank. Fuel systems that are on demand -- the in-tank pump only runs when fuel is required vs. full-time systems in which the pump runs constantly with fuel being routed back to tank by a fuel return line -- are less prone to being affected by running the tank low cause the fuel pump doesn't run as often and the fuel tank contents are not heated by the fuel returned which generally picks up heat while out of the tank. Sincerely, Macster.

Filled up the car again today at a totally different gas station (I was in a different state!) and it stopped at 11.5 gallons. I turned the handle sideways and then it filled up to 15.7 gallons. Looks like I'll just have to keep doing that when I fill up. - Anthony

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Oh noes! The toothless attendant is going all medival on you! The attendants here couldn't care less. As long as they are personally not on fire and can have their friends hang out at the store, they're all good.

Just how long is the neck of the filler tube? I know for me to get a full reading its topped off to the plastic flap area. Kind of a pain when I top it off a little too much and have the fuel in the pump nozzle adding more gas when extracting the nozzle. I just take it as when its full its full and just reset the trip odometer every filling.

During my part-time days at UPS and pumping more gallons of fuel in one day than most do in a year, gave me more insight on this phenomena than I care to mention. It's sort of a double edged sword. The reason the nozzle cuts off is simply due to one reason: The sensor/overfill-indicator at the end of the nozzle head was tripped, thus it shut off to prevent a spillage. How this sensor is tripped is the double edge sword. Apparently our tank filler-tubes are designed such that they create froth/splash and trigger the sensor. The open tank design on the tractors were never an issue unless you literally stuck the nozzle end into the fuel, then it would shut off. Since none of our tanks are spilling onto the ground, they are obviously not "full" and being tripped by the back splash or froth. Either its a tank filler tube design flaw or a nozzle design flaw. Since most nozzles are practically the same, I say its our own vehicles causing the problem. Although, it could be that some companies set/buy their sensors a little too sensitive to prevent spillage.

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While in MA, I NEVER had a problem with ANY pumps. I'm in CA for a few months and only the SHELL pumps gave me a problem. The Chevron and Mobil pumps have not. Of course, those are the only 3 brands I tried. I used to favor Shell gas in MA since Chevron is not available. Just my 2 cents.

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Glad I know that. Does the water damage injectors over time continuously, or will one hard hit do damage itself?

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Hard to say, but probably not. With port injectors they probably pass water ok with no damage or we would have heard about it by now. However, there is water and there is water. When I owned a VW TDi (turbo diesel engine with direct injection) the general feeling was to run a fuel additive that well improved the fuel. I tried it and noticed no difference and since I always bought diesel fuel at a busy stations I felt I was getting the best fuel and no addtive needed. But once when I was tipping a bottle just before filling fuel tank I looked in the bottle to see how much was left and spotted a pea sized globule of some nasty rusty water. Probably the fuel filter trap would catch/trap the water and if any did make it to filter element the filter would remove the particulate matter, but some owners advised as an added step during fuel filter changes to dump a bottle of this stuff into the fuel filter housing so when you first started the engine the fuel system from the filter down through the pump to the injectors would get a nice dose of fuel system additive/cleaner. Trouble is this could put that globule of water right into the most critical water/dirt sensitive portion of the fuel system. With gasoline DFI and the much higher fuel pressures and multiple shots of fuel the injectors might be damaged if a large slug of water passed through one. When I have a VW TDi with a diesel engine the concern was not only for the injectors but the fuel pump. The fuel pump on a diesel engine is a work of art and expensive as H*ll. For gasoline DFI engines I do not know how sensitive, or even if they are sensitive at all, the high pressure fuel pump is to water. My belief is if it not too much trouble to avoid finding out, it is best to avoid finding out. And for me it is not too much trouble to avoid running the fuel level in the fuel tank down way low. And I don't auto-x my car but if I did I'd run a 1/2 or more fuel tank and suffer the penalty of the added weight. Sincerely, Macster.

Mine is at the dealer for this situation of not taking in any fuel. I tried 3 pumps at 2 different stations this morning and it just kept spitting back out. Luckily I was very close to the dealer. We'll see if the CPO covers it.

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Strange with 3 different pumps. I do notice some times I get trouble from some pumps. I've started doing what I do with my bike and before putting the nozzle in the cars tank I tip the fuel nozzle down to drain and fuel the ports are holding onto the ground. Yah sure I paid my tax enough for them to handle the clean up but some times the nozzles have a lot of fuel in them and I suspect its its fuel in the little line that controls kicking the pump off when it senses fuel being sucked up int it. I see it as so many people go for a super full tank before another price hike. Then they don't want green peace to burn a cross on their front lawn so they don't spill any of the fuel that was sucked up the cut off sensor tube. That is the closest I can figure it. Oh yah, my gauge is still screwed and doesn't register full at kick off. There is a good reason to not keep jamming the tank full which is a CEL light from the activated charcoal filter for over flow being full which does a shut off valve yada yada. So just semi double tap at fill up time.

Watch out. I tried filling mine too much and then started watching an accident that ws going on between a mazarati and a civic....gas started poring out all over my brand new shoes. I ruined my shoes and got high on the way back to work.

Theres a plastic ring you can get from the dealer that helps the backpreseure from kicking out the pump nozzle i have a 997.2 an we get the same problems.

Thread necromancer strikes again!

Yes. I had similar issues. My issues eventually turned into a drivability issue with a no start condition after words. I also had issue where it would also "over flow" the tank and spit gas out all over me at the same time. After blaming the gas pump and going to another station I found my car was the problem. But I still didn�t fix it. I drove it till the car wouldn�t run anymore. I have no idea how with the gas cap off, this was the issue, But it was. I did the fix 6K miles ago and the car was perfect. I was also getting a CEL at idle sometimes. I forget what the code was. However my issue was a valve located in the engine bay just left of the TB. This valve controls the amount of vacuum that is applied to the gas tank. The valve was sticking open. Thus putting a lot of vacc on the tank and starving the engine of fuel. What this had to do with my filler issues, I have no idea. But I replaced that valve and it all went away and the car as been fine

i have simply given up on this issue. i thought i had figured out the golden key and was exciting to start my 2nd thread...except the 3rd time i tried the following, it didn't work. By accident, the pump went off with putting in only 1 gallon. I turned it back on and it took 14.5 gallons for a total of 15.5!!! My car had never taken that much b4. next time i filled up i did the samething; put it 1 gallon, turned the pump off, then restarted and it took another 14 before stopping. Rocket scientist! Then i tried it for the 3rd time, same station, same upside down handle, and wa lah...nothing....12.7 gallons. Even if i wait, when i try to fill up past the 12 to 13 gallons, gas overflows. i read the whole article on the zip tie thingy around the tube. i'll look at my e6 fuse 2day. With all the experts & engineers on board here, and i say that without being sarcastic, why can't someone figure this one out! thanks as always! m

I had a similar problem. I tried the upside down fuel nozzle and it worked perfectly. For anyone reading this post, try that first - its simple and, from the reading I have done, pretty effective.

After talking with a couple of 996 owners and noting numerous rennlist comments on the subject of trying to fill my 996's tank completely, I have concluded that 996s have a tank venting "issue". The effect is once attaining about a 3/4's fill, the last 1/4 fill can be a lesson in frustration sometimes. I have finally written this "issue" off as part of the 996's charm. relinuca