Pump accuracy

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Oct 11, 2002
Colorado Springs
I searched google and came up with this. It is a possibility if you kept pumping past the automatic shutoff and the car was absolutely running on fumes when you pulled into the gas station. Vehicle fuel tanks are supposed to have a space of air above the fuel in the tank as part of the evaporative emissions system and you may have filled that portion with fuel. If you really know your car and how much fuel it takes and you regularly do a couple clicks past the automatic shutoff on the pump, I'd be ******!
are you sure it doesnt claim that its a 14.5 gal tank... with a x.y gallon reserve?

Thats how my MB and BMW tanks are stated.

The reserve is irrelevant to the "tank volume" in the way they report it.

I ran it dry the time I found out that I didn't have a 15 gallon tank as I assumed. Based on what I put in then, and I filled it very full, I concluded it had a 14.5 gallon tank and looked it up. Yep, 14.5 gallons.

Everything was on level ground, so no odd changes that way. I really believe the pump is seriously out of calibration, but don't want to be making wild accusations.

Both of my last two cars, 2001 Toyota Corolla and 2005 Honda Civic can hold significantly more than the stated tank capacaity if you keep pumping after the automatic shut off. Both quote 13.2 gallons but I've pumped over 14 in both already when they weren't even completely empty.
Complain to the weights & measuries athorities over this? Just what we need is more government intervention for the auto industries. Get a life
If you report this to the state, they should send someone out to actually measure the pump calibration. They'll pump a certain amount of gas into a calibrated container and see how the pump measures up. Based on that, they'll decide what to do about it. Anything you report won't stand up in court, but it's good enough for them to come out and check in a way that will. I wouldn't worry about false accusations. The state should be making sure it's really off before they take action.

Originally posted by Eddie:
Complain to the weights & measuries athorities over this? Just what we need is more government intervention for the auto industries. Get a life

So you're telling the guy to go ahead and let the gas station screw him out of his money? Also, how does this reflect on the auto industry? We're talking about making sure a retail establishment is using accurate measurements. That's always been important.
Take the proper one-gallon container you've accurately measured and marked a full-line back to the station. If it takes 12 more ounces to make it to the full-line, report them.
I take it Hazel Dell is in a rural area.

I heard NPR interview inspector Tim Douglas regarding this article back in March. From both the interview and the article, he stated that the speed in which fuel was pumped directlly affected the pump accuracy (and that it drove his family nuts when he filled the family car!):

"If the gas was pumped fast, consumers could still get extra fuel but also had a slightly higher chance they would be shortchanged."
The pumps here in California claim accuracy at any volume or pressure. I managed to pump 21 gallons into a 16 gallon tank about a decade ago. When I pointed the disparity out to the greasy station attendant he just silently pointed to the amount due display and lifted the handset off his phone. I paid up, drove home, and called the San Bernardino County Bureau of Weights and Measures to file a complaint. They said they'd look into it. Three weeks later on a lark I stopped into that station again and found that pump dialed back 10 cents per gallon. It wouldn't let me pump more than about 15.5 gallons into my tank, either. I used that pump for the next six months until the station was apparently allowed to reset it to the prices of the other pumps. Funny thing was that no one else was ever pulled up to that pump whenever I went in. Apparently other drivers figured the gas from that cheap pump was sub-standard during the station's "penance period". I never had any drivability problem with the gas and it was like I had my own private discount pump. The lardball station attendant? He glared everytime I paid. If I smiled back any broader, my face would've ripped open. Life can be sweet.
I have a 2006 Jetta TDI wagon. The owner's manual says it has a 14.5 gallon fuel tank. Saturday, with about 725 miles on the last tank I filled the car in Hazel Dell, Washington. It took 15.9 gallons. I figured it would take just under 14 gallons based on my driving and what the fuel gauge read.

Before I file a complaint about the pump with the weights and measures authorities, is there any remote possibility the fuel could actually have gone somewhere in the car? It was NOT on the ground, I looked. I have heard of something called a ventectomy, but have no idea what it is.


Originally posted by Eddie:
Complain to the weights & measuries athorities over this? Just what we need is more government intervention for the auto industries. Get a life

I think you misunderstood. He thinks the problem is with the pump, not the cars fuel tank.

At least in my area pumps all have to have certifications that they are accurate. Clearly it's possible for them to get mis-calibrated, either by accident or otherwise.
The circuit board that controls the pump is easy to modify. People have been caught in the San Diego area. Getting the pump to register more than it has pumped is easy. You can even set it up so that it only works when you switch it to the new setting and then you can switch it back. In this area, an owner was caught went the inspector noticed an out of place solder joint on the board. With gas prices so high, I'll bet there is a buck to be made by cheating the customer. I'm surprised that there are not more stores about people stealing gas directly from the in ground tankes.
I saw a sting (how urban legends grow
) where they knew weights and measures always used a 1 or 5 gallon container. So the pump was hacked to deliver that amount correctly but cheat on other amounts.

Maybe it would be sweet justice to buy exactly 5 gallons then re-swipe your card and buy another 5. Who knows, maybe they'll even pay a bit more in credit card processing fees.

I've read about the TDI "900 club" where you get 900 miles to the tank, apparantly by "burping" an airspace in the tank to overfill.
When I worked in stations downunder, we were checked once per annum, and every time someone complained.

Biggest problem was Commodore wagons, which had a flat tank under the boot, that while 85 litres was 65 in the owners manual (that amount was first click on a level surface).

We had one bowser with a downward slope, and it would routinely fill them.

Some customers complained to fair trading, others always filled there before trips.
I used to own a gas station, and we found that with the nozzles that have the holes around the perimeter of the tip (to suck the fuel vapor out as it is displaced by fuel entering the tank), if a person adds fuel slowly enough, the vapor return would actually suck fuel back to the station's main tank.

We first became aware of this when a customer complained that he added more fuel to his car than it could hold, so I took my Civic over to the same pump and with the customer controlling the flow, we actually put over 25 gallons into that Civic; this was with that Civic's tank 3/4 full before we started.

Needless to say, we had all of our nozzles and pumps recalibrated so that the minimum flow that could be achieved would exceed the point at which the vapor return would suck fuel back to the tank.

Essentially, the problem was caused by sensors that were insufficiently sensitive to fuel coming back up the filler tube of the vehicle, which should trigger the pump to shut off. Our nozzles required a relatively high rate of flow back up the filler tube in order to trigger the shut off.
Slightly off topic but what the heck. Guy I knew worked for company that serviced and repaired pumps. On one job he ran upon a small gas /grocery that was pumping prem out of the reg pump. Language barriers with the owner/manager made for a situation where he gave up trying to explaining it. Needless to say this station got some new customers when the word got around.
PRND3L is right about containers. Leave one full with a tight lid and it's gonna SWELL!

Weights and Measures people are already on the government payroll. Call them. If outlet is mis-vending it needs to be fixed. If it's not they probably need something to do anyway.

Eddie, what ya been smokin?

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