Filling the tank with repeatabilty

[IamIan]

Originally Posted by metromizer

the pump is measuring accurately (controlled calibrations performed (monthly?) by the State Board of Weights and Measures)

In the U.S. the department of weights and measures for each state sets , monitors , and enforces the standards for acceptable error.

There is a sticker on the pump that indicates when that specific pump was last inspected.

The old standard was 6 cubic inches per gallon ... which was pretty good ... pumps had to be within +/- about ~2.5% ... if they were off by more than that the pump would be closed down until it passed and the operator would get fined ... most states did not fine more than about ~$500 ... but it does vary from state to state.

The new standard allot of states in the U.S. are going to now is +/- 6 cubic inches per 5 gallons ... which pushes the pumps to being +/- about ~0.5% ... it still varies from state to state... some places still use the older standards ... others have lower or higher fines etc.

So if a pump were off say ~50% when it was tested once per year... the owner might get fined ~$500 ... ... and have to close that specific pump until it was fixed ... but no notices or refunds to any customers... who might have been ripped off.

Faulty pumps gouging on gas

In 2007 about ~9% of the gas pumps in Arizona failed to pass and were fined ~$300 each ... Arizona checks the pumps in the state once every ~3 years...

A disparity of 6 cubic inches draws a citation, Meissner said. There are 231 cubic inches in a gallon.

Among some of the major offenders, according to The Arizona Republic's record search:

• Six high-flow diesel pumps at Sunmart in Ehrenberg were off from 120 to 200 cubic inches in May 2007.

So for as long as 3 years there was a pump that was off 200 cubic inches out of 231 cubic inches ... a horrible ~86% error ... for sometime less than ~3 years ... and in Arizona pumps have a maximum fine... $5,000 if a pump is still off beyond that ... they reach the limit ... and in Arizona Operators have maximum fines as well ... and some maxed them out... and even though they were still in violation and their pumps were still inaccurate ... they were not allowed to be fined any more.

It depends on where you live ... I recommend contacting your state department of weights and measure and see what their policies are for pump accuracy ... and what kind of fines ... etc.

[LUVMY02CREW]

Originally Posted by cfguy2000

Filling up past the first auto-click off is just a waste of your money. The auto-shutoff valve sucks the excess gas back into the pump thinking that it won't fit in your gas tank. I was a gas station attendant for several years and I have had classes on this.

I am having a hard time believing that....can you provide some source for this info????

Maybe it's just me, but if I can see the gas, then I don't think it is getting sucked back into the pump Because if I'm understanding you accurately, then I would be able to stand there all day, continue clicking past the cutoff and never spill a drop.

Now that I think for a moment, I do believe at some stations they have a type of "vapor recovery system" that is supposed to pull the vapors back somehow to help eliminate their escape into the atmosphere as you pump....is this what you are talking about???



And, Old Tele man... thanks for the link. That had some good info in it that I'm gonna have to read through again to make sure I understand how the vapor system works.

[gone-ot]

...go to the GILBARCO VEEDER-ROOT website; they manufacture gas pump systems. Look under "fuel vapor recovery" for more info about how & why the tanks "suck" back excess fuel at the pump so as to not allow it to get into the air (especially used in California).

...here's what EPA has to say about it (text in yellow box):

http://www.epa.gov/donttopoff/

[Sularus]

good info old tele man. I knew it had to do with the EVAP system, but didn't know all the specifics.

[MGB=MPG]

humm

Air Quality Forecast Guidance for CONUS Area

[gone-ot]

...best advice, do as one of our presidents did: "...don't inhale..."

[j12piprius]

Originally Posted by Old Tele man

...go to the GILBARCO VEEDER-ROOT website; they manufacture gas pump systems. Look under "fuel vapor recovery" for more info about how & why the tanks "suck" back excess fuel at the pump so as to not allow it to get into the air (especially used in California).

...here's what EPA has to say about it (text in yellow box):

http://www.epa.gov/donttopoff/

Topping off the gas tank can result in your paying for gasoline that is fed back into the station's tanks because your gas tank is full. The gas nozzle automatically clicks off when your gas tank is full. In areas of ozone nonattainment, gas station pumps are equipped with vapor recovery systems that feed back gas vapors into their tanks to prevent vapors from escaping into the air and contributing to air pollution. Any additional gas you try to pump into your tank may be drawn into the vapor line and fed back into the station’s storage tanks.

So (1) the vapor is fed back into the station's storage tanks, regardless of much gas you get and (2) any gas you pump into your tank may also be drawn into the station's storage tanks. I don't quite get why it would only be "additional" gas. I wonder at what point this would happen, after the 1st click? the 2nd click? from the time you first put the nozzle in the tank?

If there is no difference at any time, then it doesn't matter how much the tank is filled up. If it's only when the gas reaches a certain level, then this depends on where that level might be.

Interesting, the stations might be fined a nominal amount if the pumps are found to provide less gas than paid for; however they are also encouraged to take gas back from the cars and to put it back in their storage tanks!