NO fix for Prius Gas Tank Filling Up Issues

[eestlane]

Originally Posted by richard schumacher

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

You don't top it off, right?

No, I don't. Even if I try, it doesn't take any more fuel. The problem with the nozzle seal is that gasoline flowing in somewhat pressurizes the bladder because the vapor flow rate through the vapor recovery system is somewhat restricted. Thus, the bladder is stretched larger due to the pressure (more than just the weight of the gasoline alone would do). So, when the fuel nozzle is removed and the extra pressure thus released, the bladder shrinks some and "burps" the gas on the ground.

[eestlane]

Originally Posted by landstander

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

I cut it out using an Exacto knife, holding the loosened portion with long-nose pliers so that the rubber wouldn't fall into the tank. But even if it does, it should not cause any problems; the pump suction screen will stop it.

[KAR IDEA]

eestlane, could you take of pic of that operation and post it in this thread?

[eestlane]

Originally Posted by KAR IDEA

eestlane, could you take of pic of that operation and post it in this thread?

Sorry, its all gone-gone! Actually, not much to see. Just look into the gas-fill hole and you'll see the rubber seal at the beginning of the pipe leading to the tank. Reach in and cut around it partially, then grab the loose end with long nose pliers, and cut the rest of the way. If a small piece falls into the tank, not to worry.

[Road Fan]

Originally Posted by singerlin

--- snipped! ---

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.

Ok, finally I understand, you don't necessarly care about how much fuel you put in the tank, but about checking the calibration of the MPG guage(s). So you want to know true distance and true fuel transfer into your car.

Here's my thought, and please don't take this as argumentative back-talk. How many of the potential error sources are you prepared to deal with? Can you independently measure distance, time, and fuel transfer to high enough accuracy? Clearly fuel transfer to the car is not consistent, based on the guage in the car. How accurate is the guage on the pump? Would it need to be accurate for regulatory purposes, or merely consistent for every pump in the country. Don't be mislead to assume that a display to thousandths of a gallon translates to that level of accuracy. Old mechanical pump meters showed tenths of gallons, with no reason to believe they were even that accurate.

distance: Can you or will you attach a fifth wheel sensor to your car? Standard GPS ON MOVING PLATFORMS) is not accurate below 50 to 100 meters, depending on your definition of "accurate."

Time it the only easy one.

IMO, it's not a reasonable expectation to challenge the calibration of the OEM guage, based on standard driving and pump guage fuel metering. Car engineers do it based on measured road distances and pre-measured amounts of fuel supply. In other words, for example drive a known 50-mile track supplied by a precisely measured two gallons of fuel, and when finished measure the amount of residual fuel. BTW, test track fuel is standardized, commercial pump gasoline is not. How do you compare this result to similar trials done elsewhere, at different temperatures, or with different terrain? Well, those are the next problems.

[john_dough]

eestlane--I think you are on to something with your rubber gasket removal. If that's the fix, I can understand why Toyota wouldn't implement it--they would probably lose their low emissions rating. By the way, perhaps the same result can be obtained by leaving the gasket in place and bypassing it with a straw or small diameter piece of tubing inserted with the filler nozzle each time you fill up. I might do some experimenting along those lines--the idea of removing the rubber gasket does not appeal to me. Thanks for your inputs.

[Navigator]

Originally Posted by john_dough

. . . I can understand why Toyota wouldn't implement it--they would probably lose their low emissions rating.

This point right here, I would think should concern anyone in California. I know when I get a smog check, the technician takes off the gas cap and does a visual check of everything including the gas-fill hole. It would really suck to have to buy, remove and install a bunch of parts just to replace that little rubber ring and pass a smog check.

Is this an issue? I don't know. But it sure seems worthy of some thought before cutting.

[diamondlarry]

Originally Posted by qbee42

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

This is exactly what I was saying before. The Prius system is flawed. You said that perhaps the symptoms would show up with a Prius first. Other cars out there have as good or even better emissions ratings than the Prius and don't have the problem at all. Why should other manufacturers screw up their cars like the Prius? Why doesn't Toyota just do like the other manufacturers that can meet the emissions ratings without the bladder? This is mainly what I was referring to when I talked about denying there is a flaw.

[qbee42]

Originally Posted by diamondlarry

This is exactly what I was saying before. The Prius system is flawed. You said that perhaps the symptoms would show up with a Prius first. Other cars out there have as good or even better emissions ratings than the Prius and don't have the problem at all. Why should other manufacturers screw up their cars like the Prius? Why doesn't Toyota just do like the other manufacturers that can meet the emissions ratings without the bladder? This is mainly what I was referring to when I talked about denying there is a flaw.

Sure, there are other ways to do it. The Gen I Prius didn't use the bladder, but there were some additional complications because of that.

You keep hammering on the flaw. Do you understand my point about it not being a flaw for all of us that never have trouble with refueling? It would be equally valid for me to say you keep making up all this stuff about a problem when there isn't any. I won't say that because I believe that some owners have refueling problems. You should also acknowledge that many Prius owners do not have refueling problems. It goes both ways.

Tom

[oldtown]

It is interesting that it happens EVERY fill up. To minimize this problem, I always use the slowest pump speed possible while filling up. This gives more time to allow the bladder to respond elastically and stretch more. It also can give the rubber time to warm up if the gas is coming from in-ground tanks, and warm rubber stretches better allowing more gas to get into the bladder.

It won't solve the issue, but if you are always filling up at the maximum pump speed, you are making the bladder size problem worse.

Toyota is not going to tell you how to fill up your car, they are too polite and you are the customer, so you must be right (even if you aren't).