Overfilling the gas tank

If you don't get a light you didn't cause any damage. The car will not "run poorly", you'll just get a light. There is a system in place to sense fuel between the tank and bladder and/or a leak in the bladder. It will throw a MIL/CEL or whatever you want to call it, indicating a code is stored for a problem.

Even if you did cause damage (and it looks like you didn't), there is no point in worrying about it. There is nothing you can do about it. The "fix" for damaged system components is a new fuel tank, something only done after a light appears, the code is read, and after much head scratching the dealer tech. and others decide to replace the tank.

The damage occurs -after- you fill the system to the top and let the fuel warm up (it's about 50-60 deg F in the underground tank). The fuel expands, worst case about 2-3 quarts, and forces its' way through the evap system, into the gap between the tank and bladder, perhaps even forcing a hose off its' fitting, or bursting the carbon canister (which is in the tank). This all happens because liquids are for the most part not compressible, whereas the gas "bubble" normally left at the top is. The gas bubble would compress absorbing the expansion of the fuel without producing undue pressure in the tank.

 

It is -very difficult- to siphon fuel out of a Prius. If you're really worried, make up a card to lay on the dash saying "Gas cap loose" and put it on the dash. Then loosen the gas cap. When you go to drive the car, tighten the gas cap and put the card away. Once you have burned about a gallon down from "absolutely full" there is nothing to worry about. Note that if you drive with the gas cap loose you WILL get a light (CEL or MIL). It will reset after a while once you tighten the gas cap (it may take a number of power on/off cycles, 3 as I recall). But a code will be stored that the dealer service guy will see. Also note that the fuel tank is not checked often, only every 3-5 uses of the car, as I recall. It's part of the carbon canister purge cycle.

 

Does any one know the size of the external tank, as far as volume goes. I have had it down to 1 pip and filled over 11gal a couple of times.

My thought would be, under the right conditions, the bladder would expand to this volume and it could be more than the 11.9? The stretch effect.

 

This happened to me on my 08 about six months ago, twice, and didnt hurt anything, except the enviroment I guess. The first time I blamed the pump, the 2nd time I figured it was trhe car. I no longer do anything while pumping gas, except watch the gallons. After 10 gallons it normally auto-stops, but if not, I will stop it manually.

I wouldnt worry about it.

 

The gas pump auto shut-off function can fail on any car. Usually, gas pumps shut off too early in a Prius. I guess it is a good idea to watch the pump for the one to two minutes it takes to fill up, right?

Even 30 miles after the blinking pip, I rarely get more then 9 gallons in my 2004 Prius. I drive 550-600 miles per week, so I'd like to top off the tank each fill up, but I don't want to overfill. I hope the next Prius has a bigger gas tank; maybe 13.5 gallons.

 

This is really funny. After posting this morning I went out to get groceries and fill the tank (just below 1/2). So of course it overfilled (nossle did not shut off). It attempted to burp out fuel, but I convinced it to burp vapour only (hold nossle and press down towards the ground, creating a gap in the seal above the nossle, where the vapour can escape). The fuel ended up at the filler - completely full. Put cap on, drove home (temp about 25C so lots of expansion would be expected). Of course I hit every red light, got behind every nit going slow. When I got home (5 km) I removed the cap - there was no fuel to be seen in the pipe. So if you overfill to the top and drive even a "short" distance (5 km is 3 mi) I suspect you would be fine. I left the cap loose (but sitting on the filler) just in case.

BTW, I averaged 3.5 l/100 km on the way home according to the MFD, which is what I usually see from that station. The warmup cycle is a real hit to mileage, as my tank average is running around 4.6 l/100 km.

 

No, not possible. The tank is 11.9 U.S. gallons, and the bladder is completely contained inside that volume. The net capacity is therefor less than 11.9 gallons.

Tom

 

personally, the only times i've had this happen (twice) were when i took it down to a blinking pip... anytime i've filled up at 2 pips (usually) it takes about 8-8.5 gallons and has never *knocks on wood* overfilled.

but, like i said, there were two times i took it down to a flashing pip and both times it overfilled... stupid bladder

 

BGT Syndrome, every Prius driver has experienced it at least once. I think the cause is the rubber seal that is against the filler pipe when filling. Some people have even cut that rubber seal Shut off at the first click, or sooner if you think it should already have clicked. You can go over 400 miles on a fillup with this car, what's another hundred miles worth to you, paying for a new fuel system?

 

Yeah, I'd say you overreacted. I had the same exact thought until I read about it here. I am sure both my instances were the fault of the Prius, and not the pumps. Those pumps are used 100's of times every day. I've owned my car 6 months, and have only filled up like 14 times, and twice I had gas run out. It has not happened again since I now watch the filling process like a hawk.

 

I've had problems with other cars. It's not the Prius, although the Prius is more likely to have problems with a faulty pump. If the pump is properly adjusted, you will never have any trouble.

Tom

 

Cut away the rubber seal at the top of the filler pipe, and the Prius fuels just like any other car. No more under-fills, over-fills, burp-ups, getting fuel into the charcoal canister, etc. etc. Try it, you'll like it! The downside is a small quantity of gas fumes in the air, which is better than burping a few gallons on the ground.

 

The maintenance light is a simple mileage counter. It counts miles from the last time it was reset, and starts flashing to warn you of upcoming maintenance. It is not tied into the engine or any other system.

Tom