Fuel tank top off is bad. I'm now a believer.

Well I for one am totally reformed, I didn't realize that the fuel system was that complicated. So from now on I'll round the price up and leave well enough alone. Who gave this thread 3 stars? It's definitely a 5 star thread.

 

Today it happened to me! I was pumping away and chatting with a co-woker who had pulled up behind me. The pump cut off but only 4.7 gallons had been pumped and I had gone 300 miles. The display showed I only had gotten 49 mpg so I figured the pump cut off prematurely. I tried and tried to get the pump to start without clicking off and eventually I was able to get the pump going by pulling it almost all the way out. The next thing I knew I looked up and I had pumped 7.9 gallons. It should have taken around 6.5 gallons at most. So I overfilled by about 1.5 gallons. When I pulled out the pump a very small amount of gas splash out - perhaps a couple of teaspoons. I drove the 25 miles home with the plan to siphon out a gallon or so when I got home. I cut up a hose and shoved it in the opening about 2 feet until it would go no further. I could not make contact with any gasoline! So I couldn't siphon out any gas at all.

So I definitely overfilled. But maybe only a gallon or so. I hope I didn't damage the evap system. I also hope that my garden hose didn't damage anything in my attempt top reach the gasoline. I have a scanguage and no codes so far.... Any advice?

 

If nothing has happened to me after 24K of "over" filling I would imagine you should be fine...this time anyway. :attention:

 

i wouldnt worry about a single overfill. doing it on a regular basis will get you though... plus there is a variation in the bladder flexibility due to ambient temps that will cause a variation in the volume of the tank.

 

http://priuschat.com/forums/fuel-economy/52741-gas-mileage-fuel-gauge-2.html#post719603

 

And speaking from a totally untechnical standpoint, when I first got my Prius, I learned the hard way.... not to top off the tank. I thought I could squeeze a little extra in the tank..... then when I pulled out the nozzle, gas spewed from the tank all over me!! I'm a believer now: Do not top off your tank!

 

After reading the fuel system manual, which your link provided, it appears that when fuel is added to the tank, it must be done under pressure. If this is correct, then I cannot add fuel to my Prius by just pouring gas out of a portable gas container?

 

Put an end to all your barfing and filling problems by cutting away the rubber seal at the top of the filler pipe. The seal that fits around the gas pump nozzle. Try it, you'll like it!

 

The first couple pages of this thread were interesting, though it would have been helpful to post a summary of the pdf info instead of leaving the casual reader guessing.

What's amazing is that I have looked at priuschat for two years now and I don't remember reading anything seriously warning against topping off. Like viking31, it was my routine practice, mostly for measuring fuel mileage accurately. As some reports have shown, the Prius display is not always accurate.

So, I get it now, and I hope there hasn't been any damage to my fuel tank or the vapor system. And, like viking 31, I think Toyota ought to and can design and build a better system that isn't so fragile.

 

I haven't reread this entire thread but I'd seen enough posts about people having fuel get burped out when trying to top off. (I've only had my Prius since January 06).

Then there was http://priuschat.com/forums/gen-ii-prius-technical-discussion/30593-gas-bladder-exposed.html.

 

They fixed this on the 3rd gen prius, it doesn't have a bladder anymore.

 

Since I have a GEN III I believe there is still a commentary about "NOT TOPPING OFF" when fueling...

So, even though this GEN III does not have the bladder I feel safer not pushing more into the tank.

It still has the evaporative recovery and don't know what affect that could have on that as well.

So rather be SAFE than SORRY....

 

Bob u r correct. there is still a vent tube that doubles as an overflow tube by default. this will cause fluid fuel to clog the filter in the vapor recovery cannister.

now, only guessing as to possible problems. but a clogged filter means greater back pressure which means a harder working fuel pump (not easily or CHEAPLY replaceable btw) which may not last as long as it should.

not to mention a possible spill. many reasons not to against getting what?? an additional 20 miles on a tank of gas??

 

I've read this thread before and I never top off. With 120K+ miles, I filled up today and after the gas-pump click I pulled the gas nozzle out of my 06 Prius and the gas tank starting "barfing" gas out. Probably about a pint of gas for several seconds. This never happened before ever for me.

I had never used this new gas station before so maybe the pumps are too powerful, or maybe I did not have the gas pump in the tank all the way.

I'm going to watch this next time I fill up.

Any ideas?
Thanks
Dave