Spewing Fuel

Built up air pressure. That's why gas stations post "no top off" signs. The emptier your tank is, the more air pressure bulids in. Most newer (5 or 6 years) hoses are designed to recover the built up vapor to prevent it from spewing. Usually, I top of just to get a round dollar amount. That can happen with any vehicle, it's not a Prius thing.

 

you just managed to streach the bladder and when the nozzle came out the bladder relaxed and the fuel came out. Normally I just hit it a couple of clicks and round off to the nearest 2 bits and call it a fill up. What happened is pretty well normal for a bladder.

 

Same thing happened to me, and I was so excited too that I had 11.04 gallons filled into the tank - until it came back out. While it would be nice to "just round to the nearest dollar", that would mean no more than 7 or 8 gallons for me, and that's not acceptable, especially when I know that's not filled. The last tank I was able to get 10 gallons with no backsplash. I just suggest slow careful filling as best as you can - unless of course you're ok with only getting 3/4's of a tank each time.

-m.

 

Yes, this is a very sad occurence. Losing a half a gallon of fuel pretty much undoes any environmental 'benefit' of the car.

There is so little to be gained and so much to be lost when we try to force fuel into the tank. The auto shut off is there for a reason and trying to subvert it is just plain wasteful and destructive to the air that we all breathe.

Wayne Brown once posted that it is estimated that with a lifetime of fillups (10 years) on a Prius there will be 7 ounces of gasoline wasted through evaporative emissions ...

I am resigned to smaller fillups (6 gallons earlier this week). Luckily, with the fabulous mileage, my range is almost twice that of my old car! Half as many fillups means half as much VOCs from evaporative emissions at refuelling!

 

The following is for people who want to carry all the gas their tank can supposedly carry. All other just avert your eyes.

Some people have made comments about taking too long to add gas being a waste of time, but I still do it slowly anyway.

The last couple of times, I found I could only get within 3 gallons of full at full speed, then had to nurse in the rest. I notice no gurgling sound while this is going on, which used to warn me on other cars that the filler pipe was backing up and I should slow down. That filler hole seal isn't sound-friendly

At the point of having the filler click off very quickly, my best suggestion is to put in 25 cents worth of gas, stop, pull out the filler, and see if the gasoline is still visible. Repeat, and QUIT when you see gasoline bubbling for even a moment. It takes a while, but in my case the spillage seems to have gone down.

NOW, if you find a broken filler and don't notice it isn't working to quit under pressure, you WILL spew gas because it won't stop and the pressure will be enormous. It happened to me a couple of times, where I was going "Gee, I didn't think I could put *that* much gas in", and it didn't stay in. If the filler never clicks at all for over 8 gallons, be darn careful...

Note: lately, using 25 cents as the add amount has worked out well, since every time I fill up, 25 cents is less and less gas to spill. Someday, if it ever moves back to a larger amount of fuel, I'll have to go to 20 cents or so...

 

The exact same splashback problem happened to me on my second fill-up last Saturday. After running the pump at half speed for the until it clicked off at around 9 gallons, I trickled the gas in until around 10.2 gallons I too heard the ominous gurgle and it spit up perhaps half a cup or so of gas before I quickly screwed the gas cap back on. :roll:

 

:roll: Happened to me today. Learned my lesson.

 

That's why I never top off. Since I never have to use cash any more (pay at the pump with my credit card), there's no reason to. I have a feeling people still try to get that round number, though, even when they use a credit card or check card. Old habits are hard to break

 

I have posted a few different web sites regarding not topping off. They can be found at http://home.earthlink.net/~jkash1/#misc

I have to admit I didn't listen to the advice last time I got gas and did spill a little. I would rather have to get gas a couple of days earlier than to spill it again, so I won't be trying to top off anymore.

Jeff

 

The last tank when I took my time - probably 10 minutes to fill - has given me so far at least 3 extra days between fillings. As long as I know enough to be careful and not to spill any, it's worth the extra ten minutes for me to be able to go 10+ days without filling as opposed to 7 days or less.

-m.

 

My new record (that I've noted) for having the first bar go out is 194 miles. This took a while of cramming gas in, plus decent MPGs on the highway...

 

Reading through the articles regarding pump inaccuracies, I came across this sad revelation that I did not realize:

"Don't top off your tank. If you try to put extra gas in after the automatic shut off valve activates, you may be pouring it back into the station's underground storage tank through the vapor-recovery line. Topping your tank may also block the vapor-recovery line, causing problems for the next customer. "

Now, blocking the vapor recovery line isn't too big of a deal - it clears itself after a few clicks for the next customer. However, the fact that the gas would be travelling back into the tanks, and still registering on the meter, that's what really bothers me. Does anyone know if it's just the 'vapors' that are being pulled back, or is it worse like I assume, and actually using the vapor line to pull gas back in? Anyone with more info about the Vapor Recovery Systems at gas stations feel free to let me know!

-m.

 

so what we are saying here is that prius bladders burp, and occasionally have acid reflux. great. what's next, they break wind?? (that was the nicest way i could think of to say that...)

 

haha! Well, apparently this isn't because of the Prius 'bladder problems', it's regarding the Vapor Recovery System of gas stations used to reduce gasoline vapors from polluting the air.

-m.

 

i don't know, i suspect that it might be some combination of the vapor recovery and maybe a little flexing on the part of the bladder...

 

The vapor recovery system is just that - a vacuum pump of sorts that is supposed to remove the volume of air displaced when the fuel is added, which is partly fuel vapor, to be condensed and reused as fuel. When you top off, as liquids are denser than air, the vapor recovery system can become blocked, as it is not intended to syphon fuel through it. It will quickly clear, but can result in fuel spilling from the filler nozzle.

The prius is rather interesting. With the bladder, the vapor recovery is essentially not operating, and may be creating a slight vacuum. When you top off, the surge of pressure vs vacuum with only a small area remaining to damp the impulse energy may be causing bladder movement, thus the resulting upchuck. At the very least, the dissolved oxygen or co2 in the fuel may be upset, as the vacuum to pressure transition may cause a rapid change in the net dissolved capacity. If you have ever watched fuel exit a nozzle into a container, you will remember the fuel comes out almost as foam. This may also contribute to the burp, depending on the rate of flow and the vacuum pull from the recovery system.

Here in Michigan where I am, we do not have vapor recovery systems. I have had no burps to date, but have only refueled a few times and have been careful as a result of other's reported experiences.

By the way, back in the early 90's reports suggested the vapor recovery systems returned nearly 5% of the pumped volume of fuel to the delivery system in the form of vapor. It was hard for me to believe the resistance some had to the systems when many ultimately paid for themselves in a short time.

 

Take this simple quiz: have any of you *ever* had any upchuck spilllage when you were *not* trying to top off?

 

Actually, I almost did, and I don't know why I didn't.

I usually fill up at the same station, same pump. Set it on slowest fill and after it shuts off the first time, manually fill slowly to second clickoff then stop.

I have never had a burp and have never had fuel visible in the filler neck.

Last weekend I was away from home and had to fill up, so I set the nozzle on 'slow' and started doing the windows.

After a while my brain said 'this is taking too long' so I looked and I have over 9 gallons on the pump. That's FAR more than I've ever put in before, and more than I expected for the tank by a wide margin.

I clicked off the pump, and let it set for a second. I pulled out the nozzle, and the fuel was sitting right there at the top of the neck. No bubbles, no burp.

Doing the calculations it seems that the nozzle just decided to keep pumping gas out, then sucking it right back.

If I hadn't shut it off, I probably could have paid them for a hundred gallons