At the Pump

[ace rothstein 81]

When filling up your tank, has anyone else experienced the pump clicking off prematurely as if the tank was already full when it clearly shouldn't be? I have had it happen a number of times lately and I wasn't sure whether it was the gas stations or my car. This past time, I had about 11 gallons in the tank when the pump stopped.

[marleyfan]

Luckily I have never suffered from premature epumpulation.

[TrustME]

On a more serious note. I haven't had that happen to me either man.

[vpnavy]

When filling up your tank, has anyone else experienced the pump clicking off prematurely as if the tank was already full when it clearly shouldn't be? I have had it happen a number of times lately and I wasn't sure whether it was the gas stations or my car. This past time, I had about 11 gallons in the tank when the pump stopped.

I always fuel up at two different gas stations (whoever is closer when I need fuel). At one station - no problem filling up. At the other station - I have the same exact problem as you do. It probably is the gas station. Now, if you are having the same problem as different gas stations...

[KimberKenobi]

Luckily I have never suffered from premature epumpulation.

... ROFLMAO!!!

As to the other, it is most likely the pump... don't feel bad, it's not you (*snicker*)

[Woogie]

Has to be the gas station. The pump knows when to shut off from air displacement. If you look in the end of a fuel pump nozzle, you'll see two holes. One is for the gas to flow into the tank, the other for the air in the tank to vent out. When the fuel level hits the top of the tank, the air stops flowing out and the pump shuts off. Just simple physics.

[Deke40]

FYI

From howstuffworks:

How does a gasoline pump at a filling station know when the tank is full?

This mechanism has been around for a long time, so it is safe to say there is not a miniature camera inside the nozzle hooked to a microprocessor. It's purely mechanical -- and ingenious.

Near the tip of the nozzle is a small hole, and a small pipe leads back from the hole into the handle. Suction is applied to this pipe using a venturi. When the tank is not full, air is being drawn through the hole by the vacuum, and the air flows easily. When gasoline in the tank rises high enough to block the hole, a mechanical linkage in the handle senses the change in suction and flips the nozzle off.

Here's a way to think about it -- you've got a small pipe with suction being applied at one end and air flowing through the pipe easily. If you stick the free end of the pipe in a glass of water, much more suction is needed, so a vacuum develops in the middle of the pipe. That vacuum can be used to flip a lever that cuts off the nozzle.

The next time you fill up your tank, look for this hole either on the inside or the outside of the tip.

[matt_a]

It does that on our Versa also. If I try pumping the gas in too quickly it will click off way early. When it starts getting close to being full, I have to really slow down on the nozzle. Even with that, I still have to keep squeezing a little more in several times after it clicks off. Sometimes I think that's why we have inconsistent gas mileage reports on here. You never really know for sure when the tank is full. I don't want to keep squeezing it in until it runs down the side of the car. It's done this at every fill-up at several different gas stations.

[ms_stylin_versa]

It's not your car. This always use to happen with my Beetle. For some reason it doesn't seem to happen with the Versa though.

Don't worry!!!

[Versajoe]

I've filled up my Versa exactly one time. I thought the pump clicked off early. I was able to get about 1.5 gallons in after the automatic pump clicked off. I pre-paid, so I had some incentive to do so - I just barely got it to the pre-pay amount!

[KimberKenobi]

You know, even when you prepay, they will give you change... you just have to go back in... (which is a pain in the bum...) On my 'kick, I could actually tell how many gallons it would take to the decimal, so I would use a calculator to figure how much it would cost to fill (7.6 gal x $2.34 so I would hand over $17.75 - they would look at me a little funny ... ;oD)

[srellim234]

Mine probably is clicking off early, but in the long run it really doesn't matter. That does explain, however, why the first tank got 30 mpg and every tank since has been averaging at least 10% less.