NO fix for Prius Gas Tank Filling Up Issues

I tried this yesterday, applying some downward force to the nozzle which presumably creates a little gap between the nozzle and the o-ring on the filler neck. I stopped filling after 6.5 gallons because I started to hear the sound of vapor being forced out. Sure enough, upon inserting the nozzle normally and pumping again it clicked off immediately. So I guess it works but it's probably not a great thing to do since this puts hydrocarbons in the air instead of the charcoal cannister.

Here's to hoping for a bladder-free tank on the 2010!

 

Its not how you hold the lever. Its not the pump. Its not the gas station. The bladder works fine. After my first gas belching I thought about the way I fuel and whats forcing the fuel out or refusing to allow fuel in. Its simple in that there is and will be trapped air in the bladder. You cannot fuel a gas tank with trapped air pockets. Because of the extremely tight vapor emissions recovery system in the tank.
Before you fuel let the tank vent.
When I get gas I open the gas cap. I go inside and let the tank vent for at least 2 minutes. I come back out and slow fill only. I cut a piece of wood 1 inch wide to jam under the gas fill nozzle which fills on slowest mode. On first auto click off hang the pump up. It usually now clicks off really close to what it needs. Do not try to top the tank off!!!!!
Works perfect every time...no premature shut off..no gurgling sounds..no gas belching.
I know I'm defeating the car's vapor emissions mission but whats worse..a little gas fumes or a gallon of gas on the ground.
Please try it. It works.

 

Folks, I'm an engineer, and I've designed systems that work like gas gauges and battery gauges.

You have *no* idea how much slop there is in a fuel system gauge. Here are some of the issues:

The top of the gauge is NEVER accurate. This is because it is a very bad thing for a customer to go to the gas station, fill the car to "full" and have the gas gauge not indicate "full". This generates service calls and warranty work, which is VERY expensive for Toyota to pay for. Because of this, they engineer "slop" into the gauge.

This is why the first 'cube' is showing a different amount of miles-per-cube than the rest.

The bottom 'cube' and the low-gas alarm are similarly 'fudged'-- they don't necessarily read accurately, because the penalty of having the low end inaccurate is that people are going to be stranded without gas, or worse, driving their Prius on battery-only, which is a *bad* idea.

You also have to understand that the fuel sender-cable-gauge arrangement is not very inherently accurate. Your typical fuel sender in the gas tank is an arrangement roughly like the valve in your toilet-- it floats on the top of the gas and gives a reading that is the height off the bottom of the tank.

You will even find, on some cars, that not even the "middle" of the tank is really the middle-- have you ever noticed on some cars (my '98 Sienna, for example) the first half a tank lasts 3/4 of the time, and the gauge *plummets* for the last half tank? This is that sensor again-- a lot of them are just a float on an arm, and when the tank starts getting empty, the float is moving more than it does when the tank is full-- which means that the "midpoint" of the tank is usually more like 2/3 full.

And don't go on to me about that fancy "digital" gauge-- it's a representation of the voltage coming out of the sensor, nothing more-- and it isn't any more accurate for being digital than a mechanical gauge. Now, on a car with onboard computer systems like the Prius, the actual method of getting the voltage from the sensor to the gauge may be all high-tech and complicated-- but that doesn't make the sensor any more accurate.

You also know that there is a damping, or "delay", in the gauge itself-- it doesn't respond to immediate changes in the fuel level, because if you did that every time you hit the brakes the fuel gauge would bounce around (before they did this, the gauge *did* bounce around-- I had a 68 Impala where I could slam on the brakes and bounce the needle of the fuel gauge off the stop at "F".) This means that you have to wait a bit before you can trust the gauge.

The reality here is that there isn't any exemption here for thinking-- the world kind of expects you to use common sense, and nature has a nasty habit of whacking those that don't.

 

Actually, on my last car, the gas cap specifically said to let the tank vent for several seconds before adding fuel-- I don't remember if the Prius says the same thing.

You're supposed to let it vent for a few minutes, at least-- the barometric pressure inside the tank and bladder may be different from the pressure outside, as well, which means you might have better or worse luck filling the tank depending on the weather and the altitude of the gas station.

 

I have an 09 Prius and with the exception of the gas tank issue, I love it. I have filled the gas tank 7 times and it has had the click-off problem 7 times. When I am anticipating putting in 8 or 9 gallons (I never let it go down lower than that in winter living here in the upper midwest), it clicks off at 4 1/2 or 5. It doesn't matter if I am filling it slowly or not. I haven't tried the upside-down gas nozzle trick yet, but will do so the next time I fill up. If I continue putting in a little at a time with it constantly clicking off and listen for the pitch change that indicates it is full, when I pull out the nozzle, air burps back and the gas starts backing up. This does not make me a happy camper.

I do object to the individual who posted the message to fill it up until it shuts off and just go for 300 miles. I want to know what kind of MPG I am truly getting and you cannot get that from the internal gauge. The only way to get it accurately is to fill the tank completely, measure the miles and fill it completely again. If you never know if you have completely filled the tank, you don't know how accurate the MPG is.

 

Knowing how much you actually use in fuel should not be a problem. If my consumption on the screen indicates that I've travelled 400 kilometers since my last fill up and I pump 20 litres of fuel according to the pump or gas receipt than I calculate that I've used 5.0 litres per 100 kilometers. 400 divided by 100 = 4 20 divided by 4 = 5. I've done this numerous times to check the accuracy of the consumption screen and it is always correct.

 

Remove the rubber seal at the top of the gas filler pipe and your filling and burping problems will be over.

 

At the cost of increasing evaporative emissions from the tank and water vapor infiltration into the tank. Better to be patient when filling and try another pump if you have a problem.

 

First off, I want to say that I agree with you on everything you said. Secondly, you are wasting your time talking about this here because most of the people here deny there is a problem and will say something like try another pump; it won't help. The only way to solve this problem is for Toyota to wake up and get rid of the bladder like the other car companies did that meet or exceed the emissions level of the Prius. Other than this or the traction control issue, I love my Prius.

 

So, do you suppose that some Prius have this problem, and some don't? This is a serious question. I am one of the posters who properly claim the problem doesn't exist, at least with my Prius. I suspect that is the case with all of the posters who claim there isn't a problem: it just means that there isn't a problem with their Prius and/or gas pumps.

I seriously doubt that we have a conspiracy of Prius owners trying to hide a fueling problem.

To my way of thinking, the problem is either with some Prius, some pumps, or some owners. The hard part is telling the real problem or combination of problems.

Tom

 

Time for an EBH mounted on the underside of the gasoline tank or a light bulb, turned on and laid on the ground under the tank? This works some times in extreme cold (-40 °C) when gasoline is reluctant to move.

 

The problem does exist. It has happened to me before(occasionally but not always) but, from the information on this forum, I know how to get around it. For example, I was on a flashing pip once and the stupid pump kept shutting off after ~.1 gallons or less.(What do the people who say to pump until it shuts off and hang up the pump in this situation?) I know what you're going to say: Try another pump, right? I use the same pump at the same station every time. I have filled without problems and filled with problems at the same pump. The annoying part is that I haven't found any logical pattern to when the problem will occur. I wouldn't say people are trying to cover up the problem so much as denying it exists. I have never heard of any other car having this issue at the rate of the Prius. The bladder was a stupid idea. Period. It's not necessary to meet AT-PZEV emissions since other cars can without it.

 

Sorry that I didn't make it clear what seal. Not the gas cap seal, that would indeed cause the problems you state. I am referring to the seal that fits tightly around the gas pump nozzle during refueling. Sure, some gas fumes will escape during fueling, but that is better than spilling a pint or two on the ground when the bladder "burps" when the nozzle is removed. The gas tank is still totally sealed when the gas cap is tightened.

 

Ah. Hmm, yeah, probably better that than even one burp.

You don't top it off, right?

 

Perhaps you missed my point. Just in case, I will state it again: Those of us that don't have this problem don't have a problem. It's as simple as that. I am willing to take your word for it, as well as the other sufferers, but it does beg the question as to why some Prius owners have this problem while others don't. I can't help you because I have never experience a random filling problem. The only time I have ever had trouble was with a bad pump nozzle. I have actually had less trouble with refueling my Prius than with my other, non-bladder car.

My guess is that the sealed tank system on the Prius generates a bit more back pressure during refueling. This means that any touchy pump nozzle will be more likely to kick off early. I suspect, but have no way of knowing, that some parts of the country have pumps with differing characteristics. It's only a guess, but seems plausible.

If other vehicles used a tank system similar to the Prius, then gas stations would adjust their pumps accordingly. Unfortunately, with the Prius tank being one of a kind, any pump problems will appear first with the Prius.

Tom

 

Just out of curiosity, did you have to cut the beastie off? Or does it simply pull off in one piece?

 

I hate the bladder tank also and I fill up mostly at the same pump. I have found turning the nozzle upside down works most of the time. I wish that it did not have that :ban: bladder. I also hate the front defrost, it should return the heating and cooling back to the previous settings when it is turn off.

 

What happens to the settings when you turn off defrost? I always run on Auto A/C. Defrost doesn't do anything funny with that setting.

Tom

 

My 2005 switches to Auto A/C when defrost is turned off, regardless of the pre-defrost setting. That's usually my desired setting anyway, so I rarely even notice these days.

 

I find that running the dual defrost/lower vent setting AC off temp set at 71f to 73f, works best in the dry colder climes. I may turn AC on if it's precipitating, and humidity seems to be building up on the windshield. Landstander, that's weird that your '05 switches like that, my '08 does not do that.

:focus:

Just my 2 cent's, I have NEVER been able to get a full 11.(whatever) gallon tank in my 08, from the get go. The most it ever took on a fill up was 10.4, and it never seems to be consistent or follow any logic. Most of the time, it takes up to 8 and 9 gallons. Now with that said, the last five tanks have been fairly illogically consistent, check it out: 8.7, 8.6, 8.7, 8.9, 8.5 and those fill ups were all from different stations and different pumps. Weird. It also seems that the outside temp doesn't matter either, because I've had 9 gallon fill ups in 90f, AND 30f.