2008 Prius Gas Tank Failure

My 2008 has 6800 miles
temperature here has been between 0 and 24 degrees for the past few week.
I was down to two pips on my gauge.
Filled up and only took 5.8 gallons.

I think there is a problem..............

haven't taken it back to the dealer yet.

 

The pump will kick off on me at about 1-2gallons but if i wait 10-30 seconds the pump will let me go and i can almost fill the tank. Temps are around 0-20F.

 

Search the forum. There are hundreds of posts relating to the gas tank, bladder, and fueling issues. I won't try to repeat everything here.

Tom

 

08 Prius here, with ~8,300 mi. --
On my last 2 fill-ups, I experienced something similar to swi66 -- Gauge indicates low on gas, but then it accepts surprisingly little, to fill it.

I'm presuming that in the cold weather (below 25-F), the bladder probably contracts. As a result of the reduced volume, less fuel is accepted.

The MFD is showing an avg of around 50 mpg, which jives with calculations.

Haven't encountered Baybutler's problem -- rather upsetting to require a bladder replacement so early!

 

This is normal. Remember that it is a small tank. With cold weather and two pips, 6 gallons is all I would expect to put in the tank.

Tom

 

Keep in mind the dealer can't replace the bladder, only the tank. The tank includes the bladder and the evap. components (which are inside).

The forum will get lonely once the 2010 models are populating the roads. They don't have a bladder, so we won't be seeing all these posts of "my tank won't fill!!!".

 

What do they have if no bladder? A regular tank like other cars?

 

The 2010 has a regular fuel tank, but that system likely also has a dedicated pump to control HC emissions, similar to Camry Hybrid and Highlander Hybrid.

 

Still waiting for my Prius, so I'm not talking from experience here, but...
The gas station stores the gas underground, which should mean it's far warmer than ambient temps now. This suggests that a winter stragedy may be to pump in a few gallons.... wait a minute or so for the warm gas to soften the bladder, then continue pumping to shutoff.
I can't test it myself for another month or so.

 

If there is some cold fuel in the bladder, then it will take a LOT of warm fuel, and a LONG time, for any warming effect on the bladder itself.

The bladder would also lose the heat immediately to the cold metal tank shell.

 

Well, the difference between the temp below ground here (about 10C) and ambient here lately (about -20C) is probably bigger than in CA. If you add say 20 l to 5l in the tank, with a bladder weighing a few kg, I would expect a temp increase of maybe 15C, which could make a difference to the flexibility here. The heat only has to work through a few mm of rubber, so I wouldn't think it would take much time. A bigger issue may be that tankers putting cold fuel into the underground tanks for a month or 2 chill the ground around those tanks a lot colder than the ground there would normally get.

 

Almost all refueling problems are from bad pumps (nozzles). The Prius bladder system puts more back pressure on the pump and nozzle. If the auto-shutoff is out of calibration, it may click off early. This can happen with normal tanks as well, but it is more likely to happen with the Prius.

Tom

 

Hmm, interesting theories. Just to "muddy the waters", I find NO difference whether I put the nossle all the way in the filler tube (sealing and therefore providing -some- pressure to expand the bladder) or hold it out and let the fuel "jump" from the nossle to the filler tube.
I don't think there is any bladder expansion caused by filler pressure. I think it's all just the weight of the fuel pushing the bladder to the tank wall (if it really ever gets much off the wall). If the bladder is cold it resists the weight of the fuel better and you don't get full bladder expansion. My theory.

Here's one for you. For the first time my guess gauge remained at 1/2 tank after I -fully- filled the fuel tank. I started by putting the nossle all the way in and running it till it cut off. Then I dribbled fuel in until it was pretty much full (still couldn't see fuel in the filler tube but it filled pretty fast (1/2 sec) at each burst I put in, so it was probably 1/2 way up the filler tube when I stopped.
Got back in the car, started up, and the guess gauge stayed at 1/2 tank, where I had started filling. It stayed there all the way home (4 km).
Next day, it showed a full tank. Funny!

 

If you have an air gap, obviously there is no back pressure. When properly inserted, the filler neck has a gasket that tightly seals around the nozzle. You can hear the air coming out of the vent as the fuel goes in. The vented air comes from around the bladder as it expands inside the metal box. As you have pointed out, it's the weight of the fuel that expands the bladder. If the bladder is stiff, it doesn't expand easily and the fuel backs up the filler neck, clicking off the nozzle. The tight seal also allows some back pressure to form, depending on fill rate and venting of the tank. This bothers some nozzles. In extreme cases, people overfill, and the back pressure forces gas to burp out when the nozzle is removed from the filler neck.

Tom

 

i will jump in to say that at 50 mpg, it does take surprising little to filler up.

now, 6 gals is a bit anemic, but not out of the question at all. i get 7.5 to 8 gals per fillup but at the same time its usually in the low 40's around here... that extra 20º does make a difference

 

I just put gas in till it stops and drive till it asks for gas again....do not know why thats so hard.....

 

ya me too. although i go from 500-600 miles per tank in summer to 350-400 in winter, it doesnt really seem to be that much of a hassle.

 

With this car, a 2007, I have learned to take a look at the nozzle end here in nozzle pollution controlled CA. I have seen bent over metal ends, and several times the rubber seal was pulled away from the part behind. I have pushed the rubber back in by hand before filling. Once I saw a chunk torn out of the rubber seal, and moved to another hose. Since I have done this, I haven't had any hard fills. Not yet anyway. Also a banged up nozzle isn't the best for the car filler hole. I guess people just drop them on the ground sometimes, or otherwise test the strength of the nozzle parts.