tank filling drama

Hopefully you didn't damage the vent system $$$.

 

I don't know why it happens. My wife was filling the tank slowly yesterday and had the same thing happened. The gas nozzle didn't shut off but she figured the car had to be full. Upon withdrawing the nozzle, between a pint and a quart of gas gushed out. I was standing right there when it happened and I cleaned up the mess.

On the other hand, the Prius has gone about 180 miles since then and the gas guage hasn't gone down one pip yet.

 

Chronic topping-off may have damaged the tank vent flap. Bummer.

 

Same thing has happened to my girl friend's 2009 at least 3 times so far. It doesn't shut off when filling and a bunch of gas comes out when you pull the nozzle out. She said she got almost 200 miles before the first bar on her gas gauge went off though...

 

This is a problem with the pump. The slow fill rate was a red flag.

Tom

 

Perhaps this is due to the flexible bladder that is the fuel tank.

I have not experienced this yet.

 

No, the tank is vented during refueling. However, the vent isn't capable of passing liquid gasoline when you overfill, hence the pressure build up and possible damage to the evaporative control system.

Tom

 

The 2010's are know for this same problem, aren't they? The dealer says my preordered prius should be in by the end of this month. It would be nice to not run into the same problem.

 

the 2010 does not have a bladder, just a tank like most other cars.

 

I have had tthe gas nozzel fail to shut off several times over filling in my 2005 model, and have not noticed any problems or complications.

 

First, it is normal for fuel to "shoot out" if the tank is overfilled. The nossle shutoff didn't work so the tank was overfilled.
Second, you won't damage anything by overfilling the tank. You -can- cause damage if you then put the cap on and it's a warm day. The fuel in the tank will expand and force itself into the evap. system, possibly popping off a hose. This is between the bladder and the hard tank and cannot be repaired. New tank time ($400+).
Third, the 2010 doesn't have this problem. It has a standard tank as stated above. You -can- overfill any tank, and I suppose you -could- overpressure any evap. system by putting the cap on when the tank was -completely- full (no air or vapour volume to take up the expansion). Fuel doesn't compress, air/vapour does, so if just fuel in there the pressure from expansion is huge.

If this happens again, you can release the pressure in the tank before removing the nossle by pressing down on the filler nossle, creating a small gap in the top. This will -slowly- allow air/vapour out (there is some in there which is what is trying to force the fuel out). You may get a bit of fuel coming out as well, but at least with this method it doesn't shoot out, trying to soak you in fuel.

The tank bladder is not a pressure balloon. It doesn't expand from pressure from the filler nossle (though I suppose it could). It expands from the weight of the fuel you pour into it. It also doesn't force fuel back out. It's the trapped air/vapour behind the fuel in the fill tube.

This has happened with Pearl twice, and there was no damage (it's been over a year since the last time and no MILs have come up). You will know if you ever do damage the system. You will get a MIL (check engine light). The system senses the fuel between the bladder and the hard tank and puts up the light.

If you do overfill the tank (you can see fuel in the fill pipe when you are done) just leave the cap on loose for a few miles. I've done this with Pearl, it didn't cause a light, it did let the fuel level drop and didn't allow expansion to over pressure the tank/system. Surprisingly I also didn't loose any fuel. Not sure why. Must be some hidden volume in there to take it up once you start moving.

 

Yes it was probably a faulty pump and with the slow fill rate it didn't trigger the cut-off properly.

BTW. One common cause for an unusually slow pump is a clogged filter. The pumps have filters and they're supposed to be replaced regularly, but sometimes they leave it too long and it can really slow the pump down.

 

Pump nozzle shutoff sensors depend on air pressure to trigger.
If the fuel is flowing very slowly, not enough differential pressure
will build up and the nozzle will have no idea. In most cars it's
supposed to be the gas reaching the level of the fill nozzle that
covers the little sensor hole in the side and triggers shutoff.
In the Prius, there's a widget up near the level of the top of the
filler pipe called the "fuel cutoff valve" that artifically creates
the necessary pressure difference to kick the pump nozzle off. I'm
not 100% sure how it works but it almost certainly depends on the
pressure created by the incoming fuel to do its thing. If the fuel
is coming in so slowly that air is leaking out elsewhere, like
around the rubber filler-neck gasket and the canister and fresh-air
valve, then the cutoff valve is never going to get the input it needs.
.
http://www.autoshop101.com/forms/Hybrid13.pdf page 3-9
.
_H*

 

I've noticed recently that my fuel gauge gets down to one bar earlier than it should, usually at about 450 miles on the tank, when I'm averaging about 48-49mpg. I think at that point, the most fuel I've been able to put in was around 10 gallons, but not much more.

At first blush, I would assume the OP found a bum pump. See what it does the next time you fill up.

 

I've had the opposite problem the past 2 fill-ups. I was down to 3 bars (well, I still am) and I couldn't even get 3 gallons of gas in the car. Try as I might, the pump would shut off right away after it hit about 2 1/2 gallons. I took out the nozzle, let it sit, tried pumping slowly, quickly -- whatever. There was no getting gas in that car this evening. And, since I couldn't get the requisite 5 gallons into the tank, the gas gauge didn't register that I have a little more fuel in the car. It's nice that the car uses such little gasoline, but it's not worth it if I can't even put the gas in that it needs. And it was 47 degrees out -- certain not so cold that the bladder should be affected that much. How did this bladder tank design continue through the entire 2G lifecycle?

 

Try another gas pump, it may have been faulty.