Does upside down gas nozzle hurt car?

No. You can hold it any way you like, as long as fuel goes into the car.

To get Pearl to fill properly I have to pull the nozzle out a bit. Otherwise the nozzle shuts off right away. I prefer this to holding it upside down. Upside down stresses the hose too much.

 

Actually it may improve your MPG by up to 50% by causing some reverse ionization in the fuel, which will then burn more efficiently. Or make the car go backwards, I'm not sure which. ;-)
But seriously, what I've heard is that you don't want to overfill or top off with the Prius, so be careful. Here in Oregon we sit in the car while the attendant pumps, so I'm never quite sure how full it gets.

- D

 

Answer:
No, The gas nozzle is a tube. As long as it goes into the fuel hole, there shouldn't be a problem.

Just don't top off.

 

umm. ok, hate to go against the tide, but at nearly every gas station in my area, it specifically states that for proper pump operation, it should be not be held upside down.

other stations state that this is required for proper auto shut off operation which my lend validation to those who say they can put more gas in the car this way. but its simply not worth the damage to the vapor recovery system that is caused by overfilling

 

Is it you or the nozzle that is upside down?

 

+1, it doesn't get any simpler then that.

 

well, before we start laughing too much, we might want to consider what the holding temperature of the gasoline is (typically 52-58º) and what the temperature of that fuel will be when its being hauled around in your car. temperature increases of 30º may increase the volume of a very full tank of gas into your vapor recovery cannister. clogging it besides having to replace a not so cheap part, may also prematurely age your fuel pump. a VERY expensive repair

http://www.pa.msu.edu/sciencet/ask_st/122591.html

For example, fuel oil tanks typically hold about 275 gallons of fuel. The filling mechanism indicates that the oil flow should be shut off when the tank is about 25 gallons short of being full to allow for fuel expansion as the temperature increases.

Auto fuel pumps also must be set so they leave a little extra room.

 

Here's what the business end of the nozzle looks like.



It is really two tubes; fuel flows into the tank through the big tube,
and air flows out of the tank through the little one. When the little one
gets covered over by the rising fuel level, the pump shuts down.
FWIW, here's what the fuel filler pipe looks like:



Rotating the nozzle might allow you to put in a bit more gas. If that's
what you're after, Withdrawing the nozzle in the pipe a little would
probably be more effective...

But there is then the possibility of the overfill problem that has been
mentioned.

Read all about the gory details of the fuel and evap system here.

 

Well, it has an interesting statement in that link
When the tank is full, the hole will be below the gasoline level and no air will pass through the pipe. A mechanical switch inside the nozzle detects when the flow of air stops and shuts off the gas.

That would mean that the fuel should be visible in the filler neck when the hose is removed as the nozzle on it is rather short. I have been sticking in a leather 1/8" string to measure how far down the fuel really is in the filler neck when it shuts off. It is a long way down, perhaps 2x-3x the length of the hose nozzle. there must be another mechanism at work.

 

If you turn the car upside-down to engage the upside-down fuel nozzle there is a possibility some fuel might leak out onto the ground.

 

There is, the breather.

If the fuel is displacing a gas, (not petrol but gaseous fuel vapours) that gas has to find a way out. It comes out through a second pipe along side the filler neck. When liquid fuel tries to go up this pipe the flow is slowed as liquid has a higher viscosity than gas, so the fuel level backs up the filler neck causing the nozzle mechanism to shut down. If you pause a few seconds some gas bubbles out through the breather and you can get a little more fuel in. This breather is placed in the tank at a level which prevents over filling as long as you stop filling when the nozzle shuts off.

 

There have been several references to "overfilling" and "topping off" the gas tank in this thread. Does anyone know Toyota's official definition for these terms? It would certainly be helpful to know what a poster means when he says don't overfill.

 

Don't go beyond the automatic cutoff on the pump. The possible complication being you force fuel outside the bladder into the clamshell containing the bladder. It's not a one to one deal, but the POSSIBILITY exists that you could damage the tank. Galaxee(sp?) detailed a customer coming in with this issue, and the repair was more than $1k to drop and add a new tank, which is the only fix.

 

I can't find an official pronouncement on what constitutes "overfilling."

But here is some additional info that cites overfilling as a bad practice:


From here.

 

I can't buy the "first click" answer. If I followed that as an official definition, every fill would leave me with only half a tank. I have to top off numerous times to get a full tank.

Regarding Galaxee's account of a damaged tank, the result was liquid fuel outside of the bladder, but the cause was undetermined.

And at the risk of hijacking the thread, I maintain that the fuel system is more robust than has been generally portrayed by the "don't overfill" advice. (Although with only a vague idea of the term overfill, the advice is largely unhelpful.) A search of PC for instances of drivers reporting damaged/replaced tanks is very enlightening.

 

Lets define "overfilling" as putting in the amount of gasoline that, when it expands, exceeds the space left over for expansion.

How do you determine when to stop? You can't, accurately. If you assume the tank holds 45 litres, that the fuel in the underground station tank is at 50F, and air temp is at 70 F, then you can calculate how much the fuel will expand (it's around 3-4 litres). But you -still- won't know if that is more than the space you tried to allow.

What happens if you do overfill? Well, the fuel will expand in the cars' tank. When it fills all the "vapour space" then it encounters "hydraulic lock" and pressure rises very rapidly. It can (and has) pop off a hose in the vapour recovery system, located between the bladder and the hard tank. This will allow fuel or fuel vapour to get in there, and that trips the "mil" lamp (enters a code in the system). The cars' system is programmed to watch for this as it could indicate a leaking bladder, and a hose off is actually a leak in the bladder system. Time for a new tank!

If you are worried that you have overfilled, you can leave the fuel cap on loosely. This will allow the fuel to expand and leak out of the tank instead of damaging the system. I've had to do this with Pearl three times now, once because I was a little too enthusiastic about getting as much fuel in there as I could, and twice because the station fuel nozzle did not shut off. BTW, the fuel DID NOT leak out. So it wasn't as full as I thought. I tighten the fuel cap once I have driven 10 km or so.
I got no codes from having the cap on loosely. I got no damage from over-pressurizing the fuel tank system (or at least no codes).

When I fill Pearl, I do so by topping off, and I top off agressively. Until I think the fuel is only a short distance down the filler tube (still can't see it, but it only takes a tiny amount of extra to bubble up to visible levels). After almost three years of this I have not seen any damage. This allows me to go 100 to 200 km further on a fillup, but more importantly, gives me a repeatable fill. That allows better estimates of fuel economy.

 

I've seen the document you've referred to. Basically it says don't overfill without explaining how to recognize when overfilling occurs - unless overfilling implies spillage.

 

Exactly, David. Your definition is intuitively good. But we cannot claim that that is Toyota's definition.

I am interested in your parenthetic comment. Is there an actual instance where a hose has popped?

Accounts such as yours confirm my contention that the fuel system can handle overfilling (at least occasionally) without striking fear into the heart of the Prius owner. It makes no sense, from an engineering standpoint, to build a fuel system so fragile and delicate that one or even habitual overfilling would result in a failure requiring a tank replacement. Also, where is the epidemic of Prius needing tank replacements? Finally, there are the claims of owners like DiamondLarry who have exceeded the nominal volume of the tank with no ill effects. I don't disbelieve him, but I sure would like to understand the mechanism.

 

Please don't leave the gas cap off loosely, your basically wasting gas. That gas in your gas tank will basically fume out of your gas tank if its loose. This evaporation is the whole reason why toyota put the bladder in.