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Sorry if this topic is too open ended I'm new to this site. I am studying engines and how they work and I keep wondering, how do cars with no gas still manage to run for a few extra miles?

If you need fuel for the combustion process to happen, and have no fuel coming through your fuel injectors how can the cylinder combustion chamber still work? I have heard the fumes left over is the cause of this but this make no sense to a novice learning about engines as the reason I explained above. How is this possible how much fuel is need to keep the vehicle moving?

P.S again if this is off topic or been done before I am sorry as I am new to this site.

  • A motor doesn't run without fuel. If your fuel indicator shows the tank is empty, there's still some fuel left. If this has been consumed, too, the motor will stall. – sweber Apr 9 '16 at 11:10
  • How much fuel do a fuel injector inject? I seen people go 10-20 miles on E? – LostPecti Apr 9 '16 at 12:58
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    In the 80s it was said that E stood for Enough – Autistic Apr 9 '16 at 13:06
  • Welcome to the site! We're glad you found us! Thanks for doing some research about what is and isn't on topic before asking. That's very cool, and isn't always easy to do, so you've already become a great contributor! If you ask a question you're not sure of, somebody will either edit it, or let you know how it might be changed to be a better fit. If it's definitely off-topic, don't get discouraged, just ask something else, or answer a question. We hope you have fun here! – Sue Apr 9 '16 at 16:42
  • Thank you sue. I am glad I found a place that can help me in my research. I am using the app and I look at it as a pocket mentor such a great community. – LostPecti Apr 9 '16 at 16:53
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The gas gauge is just an indicator and each vehicle is going to be different. I know the older Datsun Z cars had two gas gauges, one was the main one which showed the volume of gas down to 1/4 tank, while the secondary one showed from 1/4 down to empty. The secondary gas gauge was very accurate to give the driver a true indication of how much fuel was in the tank. With today's gas gauges, like I said, it's just an indicator. You as the driver need to be aware of how much fuel is left in the vehicle and understand when you need to put more fuel in. This is a practical knowledge which comes from experience. Just because the fuel gauge is pointed at "E" does not mean the fuel tank is empty, just that the quantity is getting very low.

Even vehicle with a "Distance to Empty" reading are not that accurate. You have to know, when you are below a certain threshold, there isn't much fuel left and you need to start looking for a filling station.

A vehicle cannot run without fuel. When someone says "it's running on fumes", this is just a saying. They are just stating there is very little fuel left in the tank. A vehicle cannot run on fumes. If there isn't any liquid gas in the tank (compressed natural gas - CNG - excluded), the fuel pump cannot create fuel pressure which is needed to run the engine. Fuel injected vehicles are very dependent upon the fuel pressure being correct in order to inject the correct amount of fuel per injection cycle.

  • Thanks you. That's what I thought as well this information is helpful as I'm tackling a new project.. I'm not an experience driver yet but this really helped me to understand. – LostPecti Apr 9 '16 at 13:52
  • Don't forget to vote on this if you found it helpful. – Pᴀᴜʟsᴛᴇʀ2 Apr 9 '16 at 13:53
  • I did it said once I receive 15 rep it will be public how do I do that? – LostPecti Apr 9 '16 at 14:07
  • I'm sorry, I didn't realize there was a rep cap for voting on answers which are associated with your own answer. To gain rep, you need to ask/answer questions and then people vote on them. If you have questions about how vehicles work, just start asking away. Just be cognizant of questions which pop up while asking, as many have already been asked. We love theory questions, so it will not take you long at all to have 15 reputation. – Pᴀᴜʟsᴛᴇʀ2 Apr 9 '16 at 14:11
  • Thank you I am new to this site. Glad I found a place full of people who are willing to help. – LostPecti Apr 9 '16 at 14:14
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A vehicle needs to have fuel to run, however once the tank is empty (or indicating empty) there is likely fuel left in the fuel lines, in the filters, in the swirl pot, in the float chambers and in the fuel pump. If a car is already moving, especially if it's not accelerating or if it's going down a gentle decline, it uses surprisingly little fuel. That said, once the fuel is completely exhausted, the engine will stop.

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