My Gas Tank Won't Fill All The Way

You can thank the fuel tank bladder for this issue, I have the same problem and so do many U.S. Prius owners.

 

What is your basis for making the statement "won't fill half way?" If you are basing this on seeing something like 5 or 6 gallons at the fuel pump, that's not surprising. I lived with that for the winter (filled at 2 or 3 pips) and suddently 2 fills ago I was getting 7 and 8 gallons into the tank when filling from the same indicated level.

If your basis is only seeing half full on the fuel gauge, that might be a different situation. Only once have I filled and not had it go all the way up to 10 pips. It went to 9, and went up to 10 the next morning for a brief period.

 

It's below freezing here all winter, with only the occasional warm spell. Right now it's about 27°F with two feet of snow, so I get a lot of practice fueling our Prius in cold weather. Well, not that much practice, since the Prius is so stingy with fuel. I've never had any trouble filling the tank on our Prius. It takes a little less fuel in cold weather, but the gauge always shows full when I'm done fueling. It could be your Prius, or it could be the type of nozzles used in your area.

Tom

 

<div class='quotetop'>QUOTE(Boulder Bum @ Apr 8 2007, 12:39 PM) [snapback]419833[/snapback]</div>

I believe you are the first person I've encountered that said the gauge did not show full when the pump stopped. Either it is your car or the pumps you used. If this started happening to me I would talk to the dealer as there is a way to recalibrate the gauge. The recalibration does not make it more accurate.

 

Sounds like the usual issue, but keep an eye on it. I don't think you need to be concerned unless it fights you during warmer weather (call it 50F and above).

 

<div class='quotetop'>QUOTE(Boulder Bum @ Apr 8 2007, 12:49 AM) [snapback]419741[/snapback]</div>

Define "before the tank is full".

I squeezed in 9.4 gallons yesterday. That's the most I've gotten into it since last summer. MPG based on the MFD and based on calculation were within 0.02 MPG. That's the closest I've ever seen it.

The one time I ran out of gas, it would only take 10.4 gallons. Don't expect it to actually take 11.9 gallons, except in very rare cases.

Dave M.

 

<div class='quotetop'>QUOTE(Boulder Bum @ Apr 9 2007, 12:47 AM) [snapback]420066[/snapback]</div>

Hi Boulder,

That is truely odd. Do you have vapor gas scavenging pumps at the stations there? Here we just have the seal around the nozle. The seal is supposed to push the air through the on-board vapor recovery system in standard cars. In the Prius there is not allot of air to push, as the bladder collapses as the fuel volume goes down. And what air is there expands the bladder.

With a scavenging pump (that has the suction hose rather than the seal), the vacuum generated by the hose might be too strong, and pinch off half the bladder. This is a guess. So now the fuel can only flow into half the tank.

If that is the case, try completely removing the nozzle, which will break the vacuum generated by the scavenging hose. The weight of the fuel should then unpinch the tank bladder. Then pump again. This time, the tank bladder can only collapse down onto the fuel, which will allow the added fuel to fully inflate the bladder.

My experience with the 30/40 degree F variation in tank size is that its almost exactly one gallon. Due to circumstance, I refueled in the morning at 30 F, just after the third pip went off. Then on the next tank, again just after the third pip went off, at 40 F in the afternoon, and it took an extra gallon. I was lucky that I was very close to the same gas station each time the third pip went off, and was able to use the same pump.