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The new Volts have a "hold" mode where they will hold on to their current charge and just use the gas engine. I'm sure I can run it out of gas and then have 40-50 miles to hit a gas station on a long trip (No reason to use the charge first). Is this "Bad" for the gas engine?

I'm asking this because I remember people telling me that it's typically bad to run a "Normal" car out of gas because it sucks up junk at the bottom of the gas tank that is best just left alone (Clogs gas filter/injectors).

So is it bad to run it out of gas, or perhaps good because it will stop "Sludge" from accumulating--or is the whole thing a non-issue unless your car is like 20 years old?

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    Under normal circumstances "sludge" and more usually water should be trapped in a well in the bottom of the fuel tank where the pump can't reach it. However if you habitually run your tank near empty, it can get sloshed out of the well either when driving or when you refill the tank. Of course with a non-hybrid car, you don't usually want to run close to empty in any case so this is not a big issue! – alephzero Feb 16 '17 at 22:19
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Short answer, it is bad don't do that.

Longer answer, the fuel pump is cooled by the gas in the tank and runs while the fuel system is pressurized. When you run it dry the pump can overheat which reduces its lifespan. This analysis is based on looking at a Chevy Volt fuel pump on ebay and saying from visual inspection that it was a fuel cooled model.

  • Waitasec... whose brilliant idea was it to take a fluid that is known to be both highly volatile and highly combustible, and use it as a coolant?!? Isn't that just a wee bit suicidal? – Mason Wheeler Feb 16 '17 at 22:15
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    @MasonWheeler fuel isn't combustible unless there is a source of oxygen, and it's not volatile when stored in a sealed tank. There are plenty of dumb things that have been done when designing cars, but this isn't one of them. – alephzero Feb 16 '17 at 22:30
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    @MasonWheeler the fuel cools the pump as it moves through the pump. It's as smart as taking advantage of the highly volatile sun's rays to dry your clothes. Just because the sun is very hot and can destroy things doesn't mean its use here is dangerous. – iheanyi Feb 16 '17 at 23:00
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    @MasonWheeler Petrols auto-ignition temperature is 280°C, Diesels auto-ignition temperature is 210°C. If your fuel pump is managing to approach anywhere near these numbers, the fact that you are using fuel as a method of transporting heat away is the least of your problems. – Trotski94 Feb 17 '17 at 9:19
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    @JamesTrotter: worth to mention that rockets and supersonic planes use fuel for cooling in much more critical places, namely the leading edges and exhaust nozzles! I believe this was actually one of the reasons a special fuel had to be developed for the SR-71. – leftaroundabout Feb 17 '17 at 12:43
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Probably more threatening than the reason you posted in your question about crud in the tank, is premature fuel pump failure.

Frequently running the tank low or dry could potentially cause the fuel pump to fail because most fuel pumps are typically inside the tank and are cooled by the fuel itself.

The inability to cool itself properly will cause excessive wear and early failure.

source

  • Accepted the other answer because it was 2 minutes earlier--since I can't accept both I went and up-voted a few of your other helpful answers. – Bill K Feb 16 '17 at 21:35
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I'm quite certain the other answers are relying on very old lore. Most modern fuel pumps are electric and controlled by the ECU. Most electric motors can also free run so even if they weren't shut off by the ECU when it sensed a free running condition they should be fine. I would not trust 50+ year old lore and mechanics who use hasty generalizations.

Mechanics may see 1000-10000 cars in their lifetime almost all less than ten years old with various states of repair and different owners they cannot possibly control for enough variables to make a significantly significant judgment.

You can really only trust the engineers who designed the car (the owners manual) or reports taking statistics from all over the world about modern cars (I doubt these exist).

If it is an issue the owners manual will mention it Chevy has a vested interest in making sure their cars, especially the more advanced ones, are seen as reliable.

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    Although you could be right, @Ukko specifically mentioned visually reviewing the fuel pump in question and noticing that it was liquid cooled. I'm sure you are correct that they shut off instead of just spinning but I do wonder if as the level of gas drops below the pump it might still overheat before it runs empty... Not sure what to think.. – Bill K Feb 16 '17 at 22:50
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    @BillK I can see I've already received a down-vote for not trusting mechanics, that's fine most of the people on here are mechanics and need to feel special. The problem is I might be wrong, I don't know. I've deal with a lot of electric motors in my life from little desk fans powered by a USB port to the motor that changes the filters on various satellites. And what I can tell you is that 1. Electric motors never overheat (take damage) from free-running and 2. Technology changes so fast that trusting someone who only uses anecdotal evidence is probably not wise. – user7358648 Feb 16 '17 at 22:55
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    I would also love to see someone who knows (design or production engineer or statistically backed study) and erring on the side of caution doesn't cost much. When I googled it quick about half the sites said you would ingest gunk and the other half said that was "old information" so that is another "potential problem" that might also be outdated. – user7358648 Feb 16 '17 at 23:05
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    Being a motor or electric doesn't eliminate cooling or lubrication issues. Also, the fuel pump is always working against the issue from the engine side of the fuel line, so is never in a true unloaded state. – iheanyi Feb 16 '17 at 23:33
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    Plenty of pumps, small or large, designed for liquids, will fail if you try to push air with them. It's not even always cooling, but they spin so much faster with no resistance – Chris H Feb 17 '17 at 9:18
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I have ran my tank down to where the ice is turned off automatically and I've completed my trip to the gas station on my charged battery. Today I did not Park close enough and needed to move to make the hose reach to fill it up. sufficient fuel was available for it to go through the ice startup. once that was completed it cycled off, as it has always done. Upon putting it in Drive it would go nowhere. This with the battery still half full, but no propulsion. Repeated this cycle two more times, could not move on battery power. Pushed the car to the pump and filled up. Drove away on battery power after ice went through its startup cycle of priming. Scary how I could have been stuck somewhere with plenty of battery but no ability to drive away.

  • Vehicle model year? 2013+ have the option to not use ice for heating, as long as it's above 15F. So ICE shouldnt cycle on powerup most of the time. – Ray Foss Jan 28 at 5:22
0

It's mostly fine. There is a fuel level sensor, sometimes it's faulty and it'll tell you you have fuel when you don't, but if you don't have that problem, you should be fine. The 2012 model had 14 NHTSA complaints about that. https://www.carcomplaints.com/Chevrolet/Volt/2012/fuel_system/fuel_propulsion_system.shtml

Source: https://youtu.be/QE8NiDUbRs4?t=314

This guy clearly shows there is still fuel in the lines when it kills the engines... and then goes into reserve battery power. According to my OBDII reading it's around 20% when it claims you have no battery, and 90% when it claims you're full.

  • Interesting.. I've actually had the opposite problem lately, rather than the engine dying early my Volt engine starts under certain conditions when it shouldn't and somehow the engine fully engages with the wheels immediately--the cold engine can't spin fast enough so it slows the whole car down to a crawl and pushing the gas just makes the engine try to run faster (Not healthy for a cold engine!). – Bill K Jan 30 at 22:29

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