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Ran Out Of Gas...FOUR TIMES....on Purpose....FOR SCIENCE!!!

Discussion in 'Gen 2 Prius Technical Discussion' started by Jamez P, May 16, 2023.

  1. Jamez P

    Jamez P Junior Member

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    I Prepared this experiment to gather a few key bits of data. Some hybrid related, some just "car guy" info:

    1. How empty the fuel tank really is when it flashes refuel.
    2. How many miles can I expect to drive after I get that warning. (good to know on any car)
    3. Will it KILL my Prius if I run out of gas.
    4. What is the real world capacity change of the bladder style tank hot vs. cold weather.


    First off, I did this daily driving fairly close to my home. My route is pretty flat with plenty of spots to pull off. (I had heard conflicting stories about if it would, or would not, still move under it's own power. Not testing that here.) So my plan was to coast to a shoulder as soon as it ran out. Also I won't attempt to re start, or drive the car after it runs out of gas until I put more fuel in.


    -I drove the car until one solid "pip" is shown on the fuel gauge.
    -At that point I put exactly one gallon of fuel, in a well sealed container and an OBDII scanner in the back of my car along with cheapy Hi-viz vest (just in case. I'm curious, not suicidal) and a funnel.
    -Upon hearing the "Chime"to add fuel, and single flashing pip, I re-set my trip meter.
    -Continued to drive car on commute until the "red triangle" and engine sputtered trying to start.
    -Powered off car, turned on hazzards.
    -Added 1 gallon container of fuel.
    -Applied brake, pressed power button twice. Waited for "ready" Powered off. (Did this 3 times to prime fuel system).
    -Attached scanner to clear codes (you'll usually get a cylinder misfire code as it runs out of gas).
    -Started the car and filled it at nearest gas station, made note of distance to station and quantity of fuel to fill tank. No code, no problems. The Talking Heads said it best. ..".. same as it ever was.."

    I've discovered I have a range of a low of 85 high of 107 miles I can drive on that last flashing pip.
    After driving +or-1 mile to a station, the tank will fill at 8.6ish gallons on a 80F hot day and 8.1 on a 54F colder day. So around 2 gallons is what you have on that last pip on the gauge. I've also discovered that as long as you clear your codes afterwards, it does not seem to hurt the car. I've got a more complete data set, but that's the gist of it.

    Can it be driven safely or at all after it runs out of gas? I don't know and wouldn't recommend it for the following reasons:
    1. Driving with no I.C.E. to recharge your HV battery just sounds like trouble. Will it even go into regen if your going down a hill?!
    2. If it continues to try and start the gas engine, that puts wear on a dry fuel system. Fuel cools and lubricates the injectors as well as the fuel pump. I know most cars will shut down the pump if it continues to detect zero fuel pressure. (for safety, in case of a huge leak after a crash)
    3. The engineers put that big RED triangle up for a reason right?

    So don't freak out when that last pip starts to flash, or if you run out of gas. Turns out it's quite survivable and much easier to deal with than you might think.
     
    BrokenPipe, PA Prius, bisco and 2 others like this.
  2. Tombukt2

    Tombukt2 Senior Member

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    Yes I thought we've been through all this before. But good information I've run out of the gas in my Gen 2 twice and each time I put a gallon in because it's what is in my little can in my carport and didn't have to do any priming it's an electric fuel pump that's automatic The minute you push power to the car it tries to pump fuel and pump up the rail the system whatever you want to call it. My car started right up at the first push of the button for me pulling the filler neck of my gas can out of my car and hopping in the open doors driver receipt literally seconds Hit the button and I was driving down the road headed to the gas station no need to push any extra buttons get to the gas station which is exactly 6.4 mi from my house and a sheets. Where I get the 88 Blue fuel and if I let that pump in on the second click it'll run up to about 6.7 gallons and click off from that 6.7 gallons I withdraw the neck of the handle out of the tank hole and continue filling to about 9.4 gallons at which time it will burp in a tiny bit of fuel will try to push back and run down to the tire I usually stop it with the filler tube of the pump and then I let it sit there about 8 seconds and the bladder will stop pulsating in the tank I withdraw the filler nozzle put the cap on and I'm on the move right at 10.1 gallons.
     
    Jamez P likes this.
  3. ChapmanF

    ChapmanF Senior Member

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    bwilson4web also did a bunch of the same science (maybe with a Gen 1?). Those posts should be around here somewhere.
     
    Jamez P likes this.
  4. bisco

    bisco cookie crumbler

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    i ran my 2008 out of gas by a senior moment. drove on ev until it quit completely, added 3 gallons and she fired right up.
     
    Jamez P likes this.
  5. rjparker

    rjparker Tu Humilde Sirviente

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    My gen2 ran out of gas at 60 mph but it still drove for two miles to a gas station. I was worried about it starting but it went to Ready and the engine started. However there was no battery assist and the engine alone was extremely weak for several miles.
     
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  6. SFO

    SFO Senior Member

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    "...FOR SCIENCE!!"

    Please be careful, one of our best contributors started down this same path, and now mostly posts in "fred's house of politics".
     
  7. Jamez P

    Jamez P Junior Member

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    So it will still drive for a bit on EV then? Good to know, thanks!
     
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  8. Jamez P

    Jamez P Junior Member

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    I had wondered if it would still go down the road on just battery. Good to know that in an emergency it won't just stop all together.

    In regards to how gutless a gen2 can be when the battery is low, I know just what you mean! My HV battery started to fail 60ish miles from home. It was hot out and running the AC pulled it down too far to recover. I had one red bar of battery and I could barely hit 45mph. I got a bar or two of regen on the downhills but it didn't last long. The power boost gained from the EV side of these cars makes all the difference. I think I was getting about 15mpg on that trip home, in the summer with the AC off. Brutal!
     
  9. sam spade 2

    sam spade 2 Senior Member

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    I wonder how long it will be before you need a new fuel pump ?
    Toyota warns against running completely out.
    So have several members here.
     
  10. Jamez P

    Jamez P Junior Member

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    I think I noted that concern, also the reason I primed the pump by powering it on and off a few times before driving.
    But......If I need to change a fuel pump, I will. If it does suddenly fail, I'll add that information to this post. In fact, based on your post, I'm going to not my mileage just in case. Don't really plan to run out of gas for recreation or anything. If the damage is already done, well I've got a nice shop with and lift and plenty of free time ;)

    You would think a car with so much engineering would have fixed that worry! Maybe devise a way to keep a fuel pump from killing itself by disabling the fuel pump relay. Hmmmm...
     
  11. ChapmanF

    ChapmanF Senior Member

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    It'll stop all together soon enough ... I think of the battery capacity as usually enough to go maybe several blocks at neighborhood speeds.
     
  12. Jamez P

    Jamez P Junior Member

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    Oh I'm sure! I would hesitate to drive on the EV with no way to charge, I know how much slack I have now when it flashes add fuel now. That can be an important bit of info.
     
  13. MCCOHENS

    MCCOHENS Member

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    Thanks for sharing this. Useful info, hopefully people don't start driving till the tank is empty as a regular thing. I am a little compulsive on this, driving until the refuel lite is on makes me crazy. I fill up at a quarter tank.
     
  14. Jamez P

    Jamez P Junior Member

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    I hope not either. Myself, I pass two gas stations daily on my commute so I've got no excuse to ever run out of gas. I do however take some long road trips and It's just nice to know roughly, my useful range before I can make it to the next station.