Pump it harder

Fueling up the tank of your car is never fun. Often it’s either too warm out or it’s so cold that you are freezing inside your car. It takes so much time that we often want to make it worth our while. Therefore when that fateful click happens and the pump shuts off we decide to tap of our tank, that way we won’t have to live through this misery again so soon. However, there is a reason that the automatic shut off tank exists. Not only is topping off the tank dangerous, but it can be wasteful too. The truth is that the technology behind the automatic shut off isn’t perfect. It comes with its own problems that we believe need to be adjusted to make filling up the tank cheaper and safer for all.


Why not top off your gas tank?

There are multiple problems that arise when you top off your gas tank which include mechanical issues, environments concerns, and monetary issues. When gas is input into the tank it expands and creates vapors. The vapor recovery system, required by the Environmental Protection Agency, requires that the engine utilizes these vapors during the combustion process. However, by topping off your tank, the high pressure in the tank can cause the tank to force liquid gas into the chamber that holds the fuel in vapor form. This can cause the engine to run poorly and emit higher emissions (Moor). If you continue to top off your gas the tank and chamber may have to be replaced which will by very costly. Topping off your tank degrades the environment in multiple ways. In older cars, a hole was put in gas caps so that the gas could escape and alleviate the vapor pressures exerted on the gas tank. However, these vapors cause air pollution which is why the EPA prohibited newly produced cars from having a gas cap with a hole in it. Another way that topping off your gas hurts the environment is that the extra gas can spill or leak out of the tank. This gas can vaporize and pollute the air or runoff and pollute water sources. A monetary issue that arises from topping off your gas tank is that extra money is spent on the spilled gas and repairs. Another monetary reason for not topping off your gas tank is that the fuel can be forced back into the gas station’s pump. This could lead you to pay for gas that you are not putting into your tank (Moor).

How it works right now:

Everyone has filled up their gas or at least watched someone fill up gas, and have all seen the pump shut off automatically once the tank is full. The mechanism for this is based on the principle of pressure. A venturi tube is placed inside the nozzle. This tube is designed with a narrow throat. This narrow throat causes the velocity and pressure of the liquid to change. On top of the nozzle is also a small hole. This hole is meant to allow air to flow out of the nozzle. What happens is that once the gas fluid level reaches the hole in the nozzle it blocks off the flow of air. This in return causes the pressure inside the venturi to increase. This increase in pressure creates a force that causes a diaphragm inside the pump handle to move which in return shuts off the pump (Campbell).

A big issue with the system is that it can often shut down prematurely. If there are bubbles or splashing it could cause the air hole to be blocked off which in return once again causes pressure build up in the venturi, which shuts off the pump. Also if the gas is moving quickly enough a high enough back pressure can be created which causes the pump to shut off (Campbell).


Harmful Effects:

Recent research states that per fill up 1 to 3 grams of fuel are spilled. This adds up to 1500 L per decade at a gas station (Goldman). Not only is this a lot of wasted fuel that cannot be recovered, but it can also lead to environmental issues. Since concrete is permeable fractions of the spilled gasoline are allowed to pass through the concrete foundation.  This results in the gasoline reaching the soil and potentially the ground water. This could lead to potential major health issues among humans, but also cause the destruction of ecosystems. This is due to chemicals which are present in the gasoline that are harmful such as benzene a carcinogen. This could have a bigger impact in the future since gas stations are moving from small scale stations which dispense around 100,000 gallons per month to stations which will dispense 10 times that amount (Goldman).

Proposed Improvements:

Currently, gas pumps know when to shut off automatically because of a venturi meter that runs alongside the nozzle. As stated above, the venturi meter shuts off when the airway is submerged in the gasoline, causing a pressure buildup. Splashing of the gasoline or backpressure inside of the pump can cause a pressure spike in the venturi meter that would trigger the shut-off of the pump. A possible improvement over this system could be the use of a sonar system instead of the venturi meter. Using sonar, much like a bat, to detect the distance between the nozzle and the height of the fluid.


When the distance between the receptor and the gasoline approaches zero, known by when the time between sending and receiving a signal approaches instantaneous, an electronic pulse will be sent to the pump. Shutting it off. This process would work for all types of cars and their various tank heights and widths, as the height of the gasoline is the only variable that matters. Potential issues from this would be the disturbances caused by the waves bouncing off of the sides of the tank, however, this could be resolved by shielding the receptor so that it only receives wave signals that bounce back from directly beneath it.

How would this improve life?

The improvements made by using a sonar system would be pretty helpful in many ways. The first is as mentioned above it would work for any type of tank, or container since the shape wouldn’t matter but only the fluid height. Also it would decrease the possibility of random shut offs since the design isn’t based on pressure which is harder to control, but on an actual signal created by the pump itself. This signal would not have disturbances created by itself, whereas the pressure system of the venturi could create its own disturbance and cause premature shutoff. Also this system could potentially be used to reduce any likelihood of spilling. Under the correct specifications it could be used to create a pump that can only be used when inside a container. This would be done by having the sensor only act if certain light conditions are met, such as the dark inside of a container. This would prevent people from accidentally turning on the nozzle before entering it in the container, or when removing it from the tank. It would not only be a system that would simplify the process now, but could create future breakthroughs to reduce the cost and damages caused by malfunctioning nozzles or human error.

Potential Issues:

Applying this technology to every pump at every gas station would be a very costly enterprise that would take years to complete. With alternative energy technologies working towards one day replacing fossil fuels in our cars, overhauling the infrastructure for a dying industry may not be the best option. However, this technology may have an opportunity to be implemented alongside other innovations such as liquid hydrogen refueling stations for hydrogen fuel cell cars and biodiesel and bioethanol stations.



Currently there are a lot of seemingly small issues with gas pumps, however due to the enormous size of the industry and how often people use gas stations, these problems add up. Engine knock, waste, environmental damages, and health impacts are just some of the issues that are caused by the slow compounding of gas pump misuse. Through the use of a sensor and signaling device, the use of gas stations can not only be made safer for the environment and your car, but can prolong a dying industries life by incrementally saving thousands of liters of gasoline per station per decade. Applying this technology to future innovations in the renewable energy sector can help create a future where refueling stations are safe for people and the environment. The gas station experience will never be great, but it can definitely use some improvement.



Campbell, Todd. “Answer Geek: How Gas Pumps Sense Full Tank.” ABC News. ABC News Network, n.d. Web. 23 Mar. 2017

Goldman, Jason G. “All Those Drops Add Up: Small Spills at the Gas Station.”Conservation. University of Washington, 14 Oct. 2014. Web. 24 Mar. 2017.

Moor, TNS Tom. “Why Topping off Your Gas Tank Is a Bad Idea.” Detroit Free Press. N.p., 29 June 2015. Web. 23 Mar. 2017.



  1. I have never pumped up my tank before and I definitely didn’t know anything about gas tanks so I thought it was really cool to read about the process. I think this application does make sense based on all of the negative impacts of gas stations today such as the spills and extra costs. If this method of the Sonar system really works, most of these issues with gas wouldn’t be problems anymore. Since this would be really expensive, gas station owners may not want to implement this device because they don’t want to pay for it, unless they increase the price of their gas, but then buyers can just go to other gas stations. I think the only way this idea would survive is if the government or EPA said that all gas stations needed this device to lower the environmental impact. In that case, all stations would need to invest in these new dispensers, and the economic playing field is level again. Most people just want as cheap gas as possible, and do not think so much about the environmental impacts of just filling the tank, so drivers would just find stations that have the cheapest gas, even without the device. That is why either every station needs it or none so that the gas prices increase by about the same amount.

    I think the variables would be something like the control variable being the amount of gas that can fill the tank, the manipulated variable would be maybe the nozzle to use its sonar power to detect the height and the amount of gas, and a possible disturbance variables could be that the sonar abilities malfunction and the gas just keeps coming out causing many spills. This would be a huge problem if a lot of gas spilled each use because then it would be hurting the environment even more than we are now. Some other manipulated variables could possibly be the flow of the gas into the tank, it could be slow to ensure no spilling but then people would be angry for waiting too long, or cars can just have different gas tanks to better suit filling them with gas, except this option is not realistic because of the amount of cars already produced with their own tanks already. Using sonar in the tanks we have now could definitely reduce the environmental impact by reducing spills, but the cost is the problem.

    It is definitely a great idea to have other means of filling up gas tanks in order to minimize the possible future problems. If gas is spilled, this hurts the environment as well as makes people pay more for nothing, so the sonar eliminates these problems. The underlying issue is that the hassle and cost to actually implement these nozzles at every dispenser at every station is so huge, that many stations would not want to implement them unless they were required. In the short term, the cost may be very significant and unreasonable, but in the long term, it could save thousands of dollars for customers/stations and better the environment. If cost of implementation was not an issue, every station would do it without a doubt. Overall, I think your idea is pretty substantial and it doesn’t make pumping gas any more difficult, it could actually be easier, so the technology just needs to develop to make the product very cheap.

  2. First off, thank you Sam (and whoever your other group members are), I can finally understand why my gas nozzle clicks right before my tank overflows. Initially when starting to read your post I could agree with how much it sucks to pump your gas in the freezing cold (it really does), and it’s obvious that making the pump shut off when the tank is close to full is imperative. However, I feel that your explanation for the negative effects of topping off a gas tank may have been dragged on, as you explained the current device already accounts for any issues with the tank filling up to high (the issue was that it shut off too early). With that out of the way, I will get to the actual device you proposed.

    To state my opinions early, I will say that your proposed sonar detector makes complete sense to me, in theory. I can understand why you guys would choose something that does not require a physical force to shut off the pump, as specific circumstances can change the accuracy of these devices (as in the case with the venture meter). The sonar detector would merely need to send out a signal that could give an accurate response for the gas level in the tank and then it would shut off the pump when that reading shows approximately zero. So in this sense, your sonar pulse would probably be your manipulated variable, the gas tank height your control variable, and a number of factors for your disturbance variable. Overall, the control scheme would therefore also make sense because the distance between the sensor and gas would be measured by the signal receiving time, and at a specified time (maybe t=1 second?) a control will make the decision to shut the pump off.

    Like I said earlier, theoretically this application is completely possible. However (just like the venturi meter) there could be many issues that would arrive using such a device. What if there is somehow an air pocket in the tank and the gas level is read as being higher than it really is, or what if the sonar reading is inaccurate for certain car tank shapes? Obviously, these are smaller possibilities, but these are potential drawbacks to the application. Possibly the main issue though, which you all pointed out already, is the cost of installing these devices. To replace all existing gas pumps (which would probably also be retrofitted if liquid hydrogen was ever used), would be exceedingly costly and not worth the effort to replace an already functional device. Not to mention the cost to fix a sonar sensor compared to fixing a venture meter would have a stark contrast (the sonar detector would be the costly one). All in all however, when it’s for the environment I will always say go with the more expensive alternative, even if it does provide a marginal benefit/relief for nature. Good job Sam, and his unknown partners .

  3. The idea for this blog article is a unique one in the way that it looks to improve an already existing feedback system. I think the application of the suggested feedback control system has the right intentions in mind. The desire to reduce environmental impacts of spilled gas and to cut down on the mechanical and monetary issues that can arise from topping off a gas tank is a good concern to focus on. However, I do not think that the proposed control scheme will do much to mitigate this problem. As stated in the blog, these issues arise when people try to top off their gas tanks. Even with the new proposed system, I believe costumers will still try to top off their tank since it is still an automatic shut off system. Changing the way the pump shuts off will not change the mind of the customer who is deciding to top off the tank.
    One problem that this control scheme does address is the premature shut off problem of current feedback systems implemented in pumps. The sonar technology would get rid of the pump shutting off early due to splashing or air bubbles. Therefore, I think it is possible that the sonar technology would be more accurate than the current system. This would be a helpful feature in the system however, it is not necessary for operation of the pump.
    The discussion of this control scheme did not specifically address the control, disturbance, and manipulated variables. Therefore, it was slightly difficult for me to identify what these variables were. I believe that the controlled variable was the height of the gas in the tank. The manipulated variable would then be if gas is being added to the tank or not. A disturbance variable that was addressed was the possibility of the sonar waves bouncing off the sides of the tank and causing premature shut offs. I believe the solution offered was a viable one and would get rid of this disturbance.
    The sonar sensor seeks to rid the process of accidental shut off of one of the possible disturbance variables in current pumps: splashing and air bubbles that result in pre mature shut off. While I believe the system will be effective at doing so, I do not think this product would be implemented in all gas pumps. It seems like an expensive system that would replace a current system that works perfectly fine right now. While accidental shut offs may be annoying, I do not believe the cost of replacing all of the current venturi system pumps would be worth it for gas stations. I think that it is a unique idea that would work as designed, however I do not see it being a practical solution that will be implemented. One way that the design could be improved would be if there was more of a focus on reducing the harmful environmental impacts. As I said before, I believe this system is just a different way to accomplish the same thing as current systems. Therefore, something else must be added to provide more benefits. This was addressed in the sensor that only allows for filling under certain conditions. I think that this idea is a good one and I would’ve like a little more information on this aspect.

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