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Repeatedly Running On A Low Tank?
Consider filling up your tank and not letting it drop below halfway, instead
of keeping it on low and only putting in 2 gallons here and there... http://www.foxnews.com/story/0,2933,361347,00.html Not because you could run out of gas and get stranded but because repeatedly running on low tends to ruin the fuel pump. |
Re: Repeatedly Running On A Low Tank?
Don't Taze Me, Bro! wrote:
> Consider filling up your tank and not letting it drop below halfway, instead > of keeping it on low and only putting in 2 gallons here and there... > > http://www.foxnews.com/story/0,2933,361347,00.html > > Not because you could run out of gas and get stranded but because repeatedly > running on low tends to ruin the fuel pump. > > While Fox "News" might on occasion slip and let a fact slip through their filters, I wouldn't count on it. We've been running our cars down to 1/4 or even 1/8 of a tank on a regular basis for 25 years, and have never had a fuel pump fail. I just sold my 1986 Civic Si with the original pump. It's much more important to replace the fuel filter at the recommended interval. |
Re: Repeatedly Running On A Low Tank?
Don't Taze Me, Bro! wrote:
> Consider filling up your tank and not letting it drop below halfway, instead > of keeping it on low and only putting in 2 gallons here and there... > > http://www.foxnews.com/story/0,2933,361347,00.html > > Not because you could run out of gas and get stranded but because repeatedly > running on low tends to ruin the fuel pump. I see that thing about running low on fuel damaging fuel pumps posted all over the internet, but personally I think that's total b.s. All the critical parts in the fuel pump - bearings (bushings), armature, brushes/commutator, pumping elements (vanes, rotors, or rollers) - are constantly bathed in the fuel as it flows thru the pump. That lubricates and cools the parts regardless of fuel level in the tank. With regulator bypass pumping/circulation that modern cars have, there is full volume of fuel going thru the pump at all times it is running regardless of engine demand. The only effect of low fuel in the tank is a slight temperature rise of the volume of fuel in the tank (due to same electrical power dissipated in the pump being absorbed by less mass of fuel), and that rise will be very small - power used by fuel pump is small - temperature rise of the fuel in the tank and the tank itself will be very small - lots of mass compared to the power being dissipated. *BUT* - again - the fuel is constantly flowing thru and around all internal components of the pump whenever it is running providing cooling (unless you actually run out and the engine stops - but that is a different scenario altogether, and even then, the pump will still be full of fuel at that point with a full column of fuel from its lowest end to the fuel rail - only the pickup will be filled with air, and there won't be any flow - and most cars turn the pump off when the computer senses that the engine is no longer running). If anyone wants to argue this, be sure of your facts beforehand - I used to design automotive fuel pump components. Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x') |
Re: Repeatedly Running On A Low Tank?
In article <%HP0k.6360$%Z1.4068@trnddc05>,
"Don't Taze Me, Bro!" <N00One187@NoWhere.Com> wrote: > Consider filling up your tank and not letting it drop below halfway, instead > of keeping it on low and only putting in 2 gallons here and there... > > http://www.foxnews.com/story/0,2933,361347,00.html > > Not because you could run out of gas and get stranded but because repeatedly > running on low tends to ruin the fuel pump. Um, no it won't. Interesting that the article just threw that out there with no further explanation. But then, that's Fox News for you. |
Re: Repeatedly Running On A Low Tank?
"Don't Taze Me, Bro!" <N00One187@NoWhere.Com> wrote in message news:%HP0k.6360$%Z1.4068@trnddc05... > Consider filling up your tank and not letting it drop below halfway, > instead of keeping it on low and only putting in 2 gallons here and > there... > > http://www.foxnews.com/story/0,2933,361347,00.html > > Not because you could run out of gas and get stranded but because > repeatedly running on low tends to ruin the fuel pump. It's like every "factual" story in the media is just all spin. So, is this guy an Oil Company shill trying to get us to fill-up and inflate the price of gasoline? A futures trader? A tow-truck operator? An idiot? It could be anything but the truth. There is so much unadulterated BS in the media, from NAFTA Superhighways to infomercials for Jack LaLanne Juicers. The Reader's Digest used to be the main source of of this righteous nonsense (That's Outrageous!) but now it is everywhere. Do you awaken with a painful need to urinate? You need a new drug! Do your too-small briefs leave red marks on your skin? It's cancer! My favorites are the ads for Lunesta: Side effects many include drowsiness! WTF? Sorry for the rant........... |
Re: Repeatedly Running On A Low Tank?
Enrico Fermi wrote:
> "Don't Taze Me, Bro!" <N00One187@NoWhere.Com> wrote in message > news:%HP0k.6360$%Z1.4068@trnddc05... >> Consider filling up your tank and not letting it drop below halfway, >> instead of keeping it on low and only putting in 2 gallons here and >> there... >> >> http://www.foxnews.com/story/0,2933,361347,00.html >> >> Not because you could run out of gas and get stranded but because >> repeatedly running on low tends to ruin the fuel pump. > It's like every "factual" story in the media is just all spin. So, is this > guy an Oil Company shill trying to get us to fill-up and inflate the price > of gasoline? no, that could /never/ happen. not ever. not in a million bajillion years. no sir. oh, wait, the fuel pump thing is utter bullshit, so... > A futures trader? A tow-truck operator? An idiot? It could be > anything but the truth. There is so much unadulterated BS in the media, from > NAFTA Superhighways to infomercials for Jack LaLanne Juicers. The Reader's > Digest used to be the main source of of this righteous nonsense (That's > Outrageous!) but now it is everywhere. Do you awaken with a painful need to > urinate? You need a new drug! Do your too-small briefs leave red marks on > your skin? It's cancer! My favorites are the ads for Lunesta: Side effects > many include drowsiness! WTF? Sorry for the rant........... |
Re: Repeatedly Running On A Low Tank?
On Mon, 02 Jun 2008 05:53:18 -0700, jim beam wrote:
>> It's like every "factual" story in the media is just all spin. So, is this >> guy an Oil Company shill trying to get us to fill-up and inflate the price >> of gasoline? > > no, that could /never/ happen. not ever. not in a million bajillion > years. no sir. > > oh, wait, the fuel pump thing is utter bullshit, so... Once again you show how little you know. The fuel pump is cooled by fuel. If you run on a low tank that doesn't cover the fuel pump, it can fail prematurely. At $190~425 for a fuel pump. it's probably cheaper to keep enough fuel in the tank to cool the pump. What did I expect from someone who changes his oil at 12,000 miles whether it needs it or not. Reply when you get a clue... |
Re: Repeatedly Running On A Low Tank?
On Mon, 02 Jun 2008 06:44:48 -0400, Elmo P. Shagnasty wrote:
> In article <%HP0k.6360$%Z1.4068@trnddc05>, > "Don't Taze Me, Bro!" <N00One187@NoWhere.Com> wrote: > >> Consider filling up your tank and not letting it drop below halfway, instead >> of keeping it on low and only putting in 2 gallons here and there... >> >> http://www.foxnews.com/story/0,2933,361347,00.html >> >> Not because you could run out of gas and get stranded but because repeatedly >> running on low tends to ruin the fuel pump. > > Um, no it won't. The pump is cooled by the fuel in the tank. You want to keep in enough to cover the pump. > > Interesting that the article just threw that out there with no further > explanation. But then, that's Fox News for you. |
Re: Repeatedly Running On A Low Tank?
"Bill Putney" <bptn@kinez.net> wrote
> *BUT* - again - the fuel is constantly flowing thru and > around all internal components of the pump whenever it is > running providing cooling (unless you actually run out and > the engine stops - but that is a different scenario > altogether, and even then, the pump will still be full of > fuel at that point with a full column of fuel from its > lowest end to the fuel rail - only the pickup will be > filled with air, and there won't be any flow - and most > cars turn the pump off when the computer senses that the > engine is no longer running). "most"? I would think you would want to err on the side of safety and not inconveniencing a driver with a sudden pump breakdown. Barring presentation of a study showing no detrimental effects of either regularly running on a very low tank or running to empty, I think not doing these things is easy enough and indeed an investment that costs one only a litle extra time getting gas over the life of the car. If possibly burdening the pump by forcing it to move air is not really a problem, then I remain concerned about dirt in the bottom of the tank clogging the filter and lines downstream of the pump prematurely, or possibly wearing mechanical parts on the pump, causing the pump to have to work harder, meaning it draws more current, aging electrical parts more quickly, etc. Does rust accumulate in fuel tanks? If so, does running it near empty hasten the buildup of rust? What are the leading causes of fuel pump failure? If it's "age," what exactly causes aging to accelerate? I do not want your speculation. I am well experienced in pump design myself. I want facts from a study of pump failure. |
Re: Repeatedly Running On A Low Tank?
On Jun 2, 8:05 am, "Elle" <honda.lion...@spamnocox.net> wrote:
> "Bill Putney" <b...@kinez.net> wrote > > > *BUT* - again - the fuel is constantly flowing thru and > > around all internal components of the pump whenever it is > > running providing cooling (unless you actually run out and > > the engine stops - but that is a different scenario > > altogether, and even then, the pump will still be full of > > fuel at that point with a full column of fuel from its > > lowest end to the fuel rail - only the pickup will be > > filled with air, and there won't be any flow - and most > > cars turn the pump off when the computer senses that the > > engine is no longer running). > > "most"? I would think you would want to err on the side of > safety and not inconveniencing a driver with a sudden pump > breakdown. > > Barring presentation of a study showing no detrimental > effects of either regularly running on a very low tank or > running to empty, I think not doing these things is easy > enough and indeed an investment that costs one only a litle > extra time getting gas over the life of the car. If possibly > burdening the pump by forcing it to move air is not really a > problem, then I remain concerned about dirt in the bottom of > the tank clogging the filter and lines downstream of the > pump prematurely, or possibly wearing mechanical parts on > the pump, causing the pump to have to work harder, meaning > it draws more current, aging electrical parts more quickly, > etc. > > Does rust accumulate in fuel tanks? If so, does running it > near empty hasten the buildup of rust? > > What are the leading causes of fuel pump failure? If it's > "age," what exactly causes aging to accelerate? > > I do not want your speculation. I am well experienced in > pump design myself. I want facts from a study of pump > failure. If you don't mind me breaking in to ask a question? How hot would the fuel need to become in order to accelerate the breakdown of the materials used in the fuel pumps you're familiar with? In my mind I can't imagine most materials responding in a neg- ative manner unless temperatures reach very high levels (over 200 deg. F?) as I'd imagine they are chosen for temperature resistance, among other things. dennis in nca |
Re: Repeatedly Running On A Low Tank?
On Jun 2, 2:12 am, "Don't Taze Me, Bro!" <N00One...@NoWhere.Com>
wrote: > Consider filling up your tank and not letting it drop below halfway, instead > of keeping it on low and only putting in 2 gallons here and there... > > http://www.foxnews.com/story/0,2933,361347,00.html > > Not because you could run out of gas and get stranded but because repeatedly > running on low tends to ruin the fuel pump. The fuel pump is like any other fluid pump. it requires the liquid running through it to lubricate and cool it. If you run a pump dry, its seals can burn out fast. But as long as there is fluid running through it, it will be fine. So as long as there is gas running through the pump, it won't get damaged, but I could certainly see how it could be damaged if you let it run out of gas. Just having a low tank, without the pump running dry, can't possibly cause any problems. |
Re: Repeatedly Running On A Low Tank?
"rigger" <dgrup@aol.com> wrote
On Jun 2, 8:05 am, "Elle" <honda.lion...@spamnocox.net> wrote: > Barring presentation of a study showing no detrimental > effects of either regularly running on a very low tank or > running to empty, I think not doing these things is easy > enough and indeed an investment that costs one only a > litle > extra time getting gas over the life of the car. If > possibly > burdening the pump by forcing it to move air is not really > a > problem, then I remain concerned about dirt in the bottom > of > the tank clogging the filter and lines downstream of the > pump prematurely, or possibly wearing mechanical parts on > the pump, causing the pump to have to work harder, meaning > it draws more current, aging electrical parts more > quickly, > etc. snip >>How hot would the fuel need to >>become in order to accelerate the >breakdown of the materials used in >>the fuel pumps you're familiar with? In my mind I can't imagine most materials responding in a neg- ative manner unless temperatures reach very high levels (over 200 deg. F?) as I'd imagine they are chosen for temperature resistance, among other things. I agree. I would not expect an increased fuel temperature (due, say, to the pump recircing from a low fuel tank) will have a noticeable effect on pump part wear, one because I do not expect the temperature increase to be much (as Bill indicated) and two because I think the materials are durable enough, as you wrote. I am also concerned about how the fuel's sloshing, particularly when the vehicle is turning, could tend to starve the pump, making it work harder blah blah. Granted this would have to be at very low levels. The sloshing is certainly enough that I see my 91 Civic's fuel gage go lower on left turns; higher on right turns; when the gage reads below about 1/3 tank. Way too much argues against driving to or near an empty tank. I am speaking of electric fuel pumps, by the way, which are what are used on cars with fuel injection. So anyone having an older, carbureted car likely has a mechanical fuel pump and will have somewhat different concerns. |
Re: Repeatedly Running On A Low Tank?
On Mon, 2 Jun 2008 09:26:47 -0700 (PDT), ToMh <tlhumm@hotmail.com>
wrote: >On Jun 2, 2:12 am, "Don't Taze Me, Bro!" <N00One...@NoWhere.Com> >wrote: >> Consider filling up your tank and not letting it drop below halfway, instead >> of keeping it on low and only putting in 2 gallons here and there... >> >> http://www.foxnews.com/story/0,2933,361347,00.html >> >> Not because you could run out of gas and get stranded but because repeatedly >> running on low tends to ruin the fuel pump. > >The fuel pump is like any other fluid pump. it requires the liquid >running through it to lubricate and cool it. If you run a pump dry, >its seals can burn out fast. But as long as there is fluid running >through it, it will be fine. So as long as there is gas running >through the pump, it won't get damaged, but I could certainly see how >it could be damaged if you let it run out of gas. Just having a low >tank, without the pump running dry, can't possibly cause any >problems. Hmmm.....What if the pump was getting gulps of air due to the gas sloshing around in a nearly empty tank? Is the pump pickup located in a well or a low point in the tank? Jack |
Re: Repeatedly Running On A Low Tank?
"hachiroku" <Trueno@ae86.GTS> wrote in message
news:pan.2008.06.02.14.33.51.578000@ae86.GTS... > On Mon, 02 Jun 2008 05:53:18 -0700, jim beam wrote: > >>> It's like every "factual" story in the media is just all spin. So, is >>> this >>> guy an Oil Company shill trying to get us to fill-up and inflate the >>> price >>> of gasoline? >> >> no, that could /never/ happen. not ever. not in a million bajillion >> years. no sir. >> >> oh, wait, the fuel pump thing is utter bullshit, so... > > > Once again you show how little you know. > > The fuel pump is cooled by fuel. If you run on a low tank that doesn't > cover the fuel pump, it can fail prematurely. At $190~425 for a fuel pump. > it's probably cheaper to keep enough fuel in the tank to cool the pump. > > What did I expect from someone who changes his oil at 12,000 miles whether > it needs it or not. > > Reply when you get a clue... > > Sorry to burst your bubble hachi but the level of fuel outside the pump means nothing. As has been mentioned before the fuel being pumped goes directly through the motor assembly on its way from one end of the pump to the other. This means the armature, commutator, brushes, and field magnets are all constantly bathed in flowing fuel while the pump is on. Typical construction is a steel tube containing the magnets which is crimped onto 2 end caps. The bottom end cap contains the turbine (TBI) or gerotor (MPI) pump and the top cap contains the fuel outlet, check valve, electrical terminals, and brush holders. The pressure relief valve that protects the pump from being dead-headed from a plugged filter or a kinked fuel line is also in one of the 2 caps. I have also seen pumps that were all plastic. I haven't designed pumps but I have taken apart a half dozen failed ones. All that being said I have also personally heard the distinct sound of vapor bubbles going through the fuel pressure regulator on a car with the engine running. I think in some cases the pump starts sucking air through the top of the pickup sock before the tank is completely empty but yet is still able to supply enough pressure and volume for the engine to run. P.S. Why is this cross posted to about a zillion newsgroups? |
Re: Repeatedly Running On A Low Tank?
On Jun 2, 10:11 am, Retired VIP <jackj.extradots....@windstream.net>
wrote: > On Mon, 2 Jun 2008 09:26:47 -0700 (PDT), ToMh <tlh...@hotmail.com> > wrote: > > > > >On Jun 2, 2:12 am, "Don't Taze Me, Bro!" <N00One...@NoWhere.Com> > >wrote: > >> Consider filling up your tank and not letting it drop below halfway, instead > >> of keeping it on low and only putting in 2 gallons here and there... > > >>http://www.foxnews.com/story/0,2933,361347,00.html > > >> Not because you could run out of gas and get stranded but because repeatedly > >> running on low tends to ruin the fuel pump. > > >The fuel pump is like any other fluid pump. it requires the liquid > >running through it to lubricate and cool it. If you run a pump dry, > >its seals can burn out fast. But as long as there is fluid running > >through it, it will be fine. So as long as there is gas running > >through the pump, it won't get damaged, but I could certainly see how > >it could be damaged if you let it run out of gas. Just having a low > >tank, without the pump running dry, can't possibly cause any > >problems. > > Hmmm.....What if the pump was getting gulps of air due to the gas > sloshing around in a nearly empty tank? Is the pump pickup located in > a well or a low point in the tank? > > Jack If it's getting gulps of air then that would be a problem, but the OP was talking about 1/4 tank!. |
Re: Repeatedly Running On A Low Tank?
On Jun 2, 6:34 am, Bill Putney <b...@kinez.net> wrote:
> > The only effect of low fuel in the tank is > a slight temperature rise of the volume of fuel in the tank (due to same > electrical power dissipated in the pump being absorbed by less mass of > fuel), and that rise will be very small - power used by fuel pump is > small - temperature rise of the fuel in the tank and the tank itself > will be very small - lots of mass compared to the power being dissipated. > ... > If anyone wants to argue this, be sure of your facts beforehand - I used > to design automotive fuel pump components. > GM TPI has the regulator on the outlet side of the fuel rails. Fuel returning to the tank has run all the way through the rails - which are bolted to the intake manifold. With the engine hot, you can grab the fuel rails and they'll be cold. I'll bet that makes a substantial rise in temperature inside the tank on low level. Who knows what affect that has on pump life. |
Re: Repeatedly Running On A Low Tank?
Elle wrote:
> "Bill Putney" <bptn@kinez.net> wrote > >>*BUT* - again - the fuel is constantly flowing thru and >>around all internal components of the pump whenever it is >>running providing cooling (unless you actually run out and >>the engine stops - but that is a different scenario >>altogether, and even then, the pump will still be full of >>fuel at that point with a full column of fuel from its >>lowest end to the fuel rail - only the pickup will be >>filled with air, and there won't be any flow - and most >>cars turn the pump off when the computer senses that the >>engine is no longer running). > > > "most"? I would think you would want to err on the side of > safety and not inconveniencing a driver with a sudden pump > breakdown. > > Barring presentation of a study showing no detrimental > effects of either regularly running on a very low tank or > running to empty, I think not doing these things is easy > enough and indeed an investment that costs one only a litle > extra time getting gas over the life of the car. If possibly > burdening the pump by forcing it to move air is not really a > problem, then I remain concerned about dirt in the bottom of > the tank clogging the filter and lines downstream of the > pump prematurely, or possibly wearing mechanical parts on > the pump, causing the pump to have to work harder, meaning > it draws more current, aging electrical parts more quickly, > etc. > > Does rust accumulate in fuel tanks? If so, does running it > near empty hasten the buildup of rust? > > What are the leading causes of fuel pump failure? If it's > "age," what exactly causes aging to accelerate? > > I do not want your speculation. I am well experienced in > pump design myself. I want facts from a study of pump > failure. > > It isn't a study, but my post about my experiences involves quite a few cars over several decades, and one car for 22 years. It also includes another car over 9 years. I stand by what I wrote. |
Re: Repeatedly Running On A Low Tank?
Elle wrote:
> "rigger" <dgrup@aol.com> wrote > On Jun 2, 8:05 am, "Elle" <honda.lion...@spamnocox.net> > wrote: > >>Barring presentation of a study showing no detrimental >>effects of either regularly running on a very low tank or >>running to empty, I think not doing these things is easy >>enough and indeed an investment that costs one only a >>litle >>extra time getting gas over the life of the car. If >>possibly >>burdening the pump by forcing it to move air is not really >>a >>problem, then I remain concerned about dirt in the bottom >>of >>the tank clogging the filter and lines downstream of the >>pump prematurely, or possibly wearing mechanical parts on >>the pump, causing the pump to have to work harder, meaning >>it draws more current, aging electrical parts more >>quickly, >>etc. > > snip > > >>>How hot would the fuel need to >>>become in order to accelerate the >> >>breakdown of the materials used in >> >>>the fuel pumps you're familiar with? In my mind I > > can't imagine most materials responding in a neg- > ative manner unless temperatures reach very high > levels (over 200 deg. F?) as I'd imagine they are > chosen for temperature resistance, among other > things. > > > I agree. I would not expect an increased fuel temperature > (due, say, to the pump recircing from a low fuel tank) will > have a noticeable effect on pump part wear, one because I > do not expect the temperature increase to be much (as Bill > indicated) and two because I think the materials are durable > enough, as you wrote. > > I am also concerned about how the fuel's sloshing, > particularly when the vehicle is turning, could tend to > starve the pump, making it work harder blah blah. Granted > this would have to be at very low levels. The sloshing is > certainly enough that I see my 91 Civic's fuel gage go lower > on left turns; higher on right turns; when the gage reads > below about 1/3 tank. > > Way too much argues against driving to or near an empty > tank. > > I am speaking of electric fuel pumps, by the way, which are > what are used on cars with fuel injection. So anyone having > an older, carbureted car likely has a mechanical fuel pump > and will have somewhat different concerns. > > Just to be clear: the cars I mentioned all have/had electric fuel pumps. |
Re: Repeatedly Running On A Low Tank?
The Reverend Natural Light turned on the Etch-A-Sketch and wrote:
> On Jun 2, 6:34 am, Bill Putney <b...@kinez.net> wrote: >> >> The only effect of low fuel in the tank is >> a slight temperature rise of the volume of fuel in the tank (due to same >> electrical power dissipated in the pump being absorbed by less mass of >> fuel), and that rise will be very small - power used by fuel pump is >> small - temperature rise of the fuel in the tank and the tank itself >> will be very small - lots of mass compared to the power being dissipated. >> ... >> If anyone wants to argue this, be sure of your facts beforehand - I used >> to design automotive fuel pump components. >> > > GM TPI has the regulator on the outlet side of the fuel rails. Fuel > returning to the tank has run all the way through the rails - which > are bolted to the intake manifold. With the engine hot, you can grab > the fuel rails and they'll be cold. > > I'll bet that makes a substantial rise in temperature inside the tank > on low level. Who knows what affect that has on pump life. Good point - Why doesn't someone buy me a new top of the line truck, and I'll test it out for y'all. No charge for the test. :P -- www.perfectreign.com || www.filesite.org powered by the lizard: www.opensuse.org |
Re: Repeatedly Running On A Low Tank?
"mjc13<REMOVETHIS> @verizon.net>" <"mjc13<REMOVETHIS> Elle
wrote: >> I do not want your speculation. I am well experienced in >> pump design myself. I want facts from a study of pump >> failure. > > It isn't a study, but my post about my experiences > involves quite a few cars over several decades, and one > car for 22 years. It also includes another car over 9 > years. I stand by what I wrote. Well I happen to think anecdotal experiences in certain areas, like this one, count for a lot as "data." I think maybe we can further observe that we just do not see many fuel pump failure reports here, for one. They certainly do happen, but not that often. Many factors must go into what determines fuel pump life. Maybe 1/8 tank and more is just not going to burden the pump in any significant way. Maybe the climate makes a big difference in fuel pump rate failure. E.g. climates that have a lot moisture in the air will tend to promote more rust in the fuel tank than if the climate were dry. Maybe some pump manufacturers go cheap on parts, so a chip of rust passing through the pump means it's more likely to cause the pump to fail. From talk on the net, it does seem to me that debris accumulating at the bottom of fuel tanks is not uncommon. And why have a fuel filter whose changing is prescribed to be every few years, besides, if the debris is no concern? So too do we see reports of fuel tanks failing. I do not think the OP's article is baloney. It's just suggested best operating practices to minimize fuel system problems, ISTM. Not a big deal. |
Re: Repeatedly Running On A Low Tank?
Bill Putney <bptn@kinez.net> wrote in
news:6ai0kvF37k2jlU1@mid.individual.net: > Don't Taze Me, Bro! wrote: >> Consider filling up your tank and not letting it drop below halfway, >> instead of keeping it on low and only putting in 2 gallons here and >> there... >> >> http://www.foxnews.com/story/0,2933,361347,00.html >> >> Not because you could run out of gas and get stranded but because >> repeatedly running on low tends to ruin the fuel pump. > > I see that thing about running low on fuel damaging fuel pumps posted > all over the internet, but personally I think that's total b.s. > > All the critical parts in the fuel pump - bearings (bushings), > armature, brushes/commutator, pumping elements (vanes, rotors, or > rollers) - are constantly bathed in the fuel as it flows thru the > pump. That lubricates and cools the parts regardless of fuel level in > the tank. > > With regulator bypass pumping/circulation that modern cars have, there > is full volume of fuel going thru the pump at all times it is running > regardless of engine demand. The only effect of low fuel in the tank > is a slight temperature rise of the volume of fuel in the tank (due to > same electrical power dissipated in the pump being absorbed by less > mass of fuel), and that rise will be very small - power used by fuel > pump is small - temperature rise of the fuel in the tank and the tank > itself will be very small - lots of mass compared to the power being > dissipated. > > *BUT* - again - the fuel is constantly flowing thru and around all > internal components of the pump whenever it is running providing > cooling (unless you actually run out and the engine stops - but that > is a different scenario altogether, and even then, the pump will still > be full of fuel at that point with a full column of fuel from its > lowest end to the fuel rail - only the pickup will be filled with air, > and there won't be any flow - and most cars turn the pump off when the > computer senses that the engine is no longer running). > > If anyone wants to argue this, be sure of your facts beforehand - I > used to design automotive fuel pump components. > > Bill Putney > (To reply by e-mail, replace the last letter of the alphabet in my > address with the letter 'x') I realize all I have is antidotal evidence, but in 95% of the pumps I replace, I always ask the customer and it is almost always the ones I am replacing admit to running the tank low most of the time. KB -- THUNDERSNAKE #9 Protect your rights or "Lose" them The 2nd Admendment guarantees the others |
Re: Repeatedly Running On A Low Tank?
When my Civic tank is low, it takes a lot longer to start. I've read
different theories on why. One is that a one-way valve on the fuel pump seals better when it is lubricated by fuel, so gas stays in the line. Whatever the reason, keeping the tank full puts less stress on the battery, fuel pump, and starter. |
Re: Repeatedly Running On A Low Tank?
I have noticed a slight delay in starting when the tank is
low (say 1/8 tank and less) on my 91 Civic as well. "DIYBOI" <rbrailas@courts.state.tx.us> wrote > When my Civic tank is low, it takes a lot longer to start. > I've read > different theories on why. One is that a one-way valve on > the fuel > pump seals better when it is lubricated by fuel, so gas > stays in the > line. Whatever the reason, keeping the tank full puts > less stress on > the battery, fuel pump, and starter. |
Re: Repeatedly Running On A Low Tank?
mjc13<REMOVETHIS> wrote:
> Don't Taze Me, Bro! wrote: > >> Consider filling up your tank and not letting it drop below halfway, >> instead of keeping it on low and only putting in 2 gallons here and >> there... >> >> http://www.foxnews.com/story/0,2933,361347,00.html >> >> Not because you could run out of gas and get stranded but because >> repeatedly running on low tends to ruin the fuel pump. >> > > While Fox "News" might on occasion slip and let a fact slip through > their filters, I wouldn't count on it. We've been running our cars down > to 1/4 or even 1/8 of a tank on a regular basis for 25 years, and have > never had a fuel pump fail... Same here. My daily driver Chrysler Concorde just turned 200k miles last week from its 80 mile/day commute. I run it as low as I can before filling up each time at the filling station across the street from my house - typically with the gage anywhere from 3/16 tank to below 'E'. Original fuel pump. > I just sold my 1986 Civic Si with the > original pump. It's much more important to replace the fuel filter at > the recommended interval. The Chrysler LH car fuel filter is built into the sender/pump/regulator assembly - tank would have to be dropped to replace it. But they are designed to last longer than the vehicle (barring getting some really bad/dirty gas) - no replacement interval specified - and judging from the total lack of fuel filter problems mentioned on the forums, they did a good job on the design. Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x') |
Re: Repeatedly Running On A Low Tank?
Elmo P. Shagnasty wrote:
> In article <%HP0k.6360$%Z1.4068@trnddc05>, > "Don't Taze Me, Bro!" <N00One187@NoWhere.Com> wrote: > >> Consider filling up your tank and not letting it drop below halfway, instead >> of keeping it on low and only putting in 2 gallons here and there... >> >> http://www.foxnews.com/story/0,2933,361347,00.html >> >> Not because you could run out of gas and get stranded but because repeatedly >> running on low tends to ruin the fuel pump. > > Um, no it won't. > > Interesting that the article just threw that out there with no further > explanation. But then, that's Fox News for you. Far be it from me to criticize Fox News, but in this case I agree with you. I find *all* news outlets to be totally FOS when they try to discuss technical subjects. Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x') |
Re: Repeatedly Running On A Low Tank?
hachiroku wrote:
> On Mon, 02 Jun 2008 05:53:18 -0700, jim beam wrote: > >>> It's like every "factual" story in the media is just all spin. So, is this >>> guy an Oil Company shill trying to get us to fill-up and inflate the price >>> of gasoline? >> no, that could /never/ happen. not ever. not in a million bajillion >> years. no sir. >> >> oh, wait, the fuel pump thing is utter bullshit, so... > > > Once again you show how little you know. > > The fuel pump is cooled by fuel. If you run on a low tank that doesn't > cover the fuel pump, it can fail prematurely. At $190~425 for a fuel pump. > it's probably cheaper to keep enough fuel in the tank to cool the pump. The overwhelming majority of the cooling (and *all* of the lubrication) of the pump and its internal components comes from the constant flow of fuel thru the pump and around each component. Very little cooling comes from the mostly stangant fuel surrounding the pump. Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x') |
Re: Repeatedly Running On A Low Tank?
hachiroku wrote:
> On Mon, 02 Jun 2008 06:44:48 -0400, Elmo P. Shagnasty wrote: > >> In article <%HP0k.6360$%Z1.4068@trnddc05>, >> "Don't Taze Me, Bro!" <N00One187@NoWhere.Com> wrote: >> >>> Consider filling up your tank and not letting it drop below halfway, instead >>> of keeping it on low and only putting in 2 gallons here and there... >>> >>> http://www.foxnews.com/story/0,2933,361347,00.html >>> >>> Not because you could run out of gas and get stranded but because repeatedly >>> running on low tends to ruin the fuel pump. >> Um, no it won't. > > > The pump is cooled by the fuel in the tank. You want to keep in enough to > cover the pump. Almost all cooling of the pump comes from fuel flowing thru it - very little from mostly stagnant fuel around the outside of the pump. Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x') |
Re: Repeatedly Running On A Low Tank?
Elle wrote:
> "Bill Putney" <bptn@kinez.net> wrote >> *BUT* - again - the fuel is constantly flowing thru and >> around all internal components of the pump whenever it is >> running providing cooling (unless you actually run out and >> the engine stops - but that is a different scenario >> altogether, and even then, the pump will still be full of >> fuel at that point with a full column of fuel from its >> lowest end to the fuel rail - only the pickup will be >> filled with air, and there won't be any flow - and most >> cars turn the pump off when the computer senses that the >> engine is no longer running). > > "most"? I would think you would want to err on the side of > safety and not inconveniencing a driver with a sudden pump > breakdown. The designs are not that thermally marginal to worry about. I am being facetious when I say you should only drive your car in the rain to maximize cooling of your tires, but it illustrates my point that it isn't worth worrying about. > Barring presentation of a study showing no detrimental > effects of either regularly running on a very low tank or > running to empty, I think not doing these things is easy > enough and indeed an investment that costs one only a litle > extra time getting gas over the life of the car. If possibly > burdening the pump by forcing it to move air is not really a > problem, then I remain concerned about dirt in the bottom of > the tank clogging the filter and lines downstream of the > pump prematurely, or possibly wearing mechanical parts on > the pump, causing the pump to have to work harder, meaning > it draws more current, aging electrical parts more quickly, > etc. I can't argue with that. > Does rust accumulate in fuel tanks? If so, does running it > near empty hasten the buildup of rust? Not in today's sealed (and sometimes plastic) tanks. > What are the leading causes of fuel pump failure? If it's > "age," what exactly causes aging to accelerate? Wear of the bearings (which for most pumps are actually plastic holes in pump/motor end caps (basically, plastic bushings) and wear of the brushes. Usually the plastic end caps (that act as the bearings for the armature shaft) are glass filled. The molded bearing (bushing) surfaces have a microscopically thin film of plastic separating the glass fibers from the metal shaft - an inherent result of the molding process of glass-filled plastics. Once that thin film wears thru, the very abrasive glass wears the metal shaft faster than the plastic itself wears believe it or not (I learned this when I worked as a designer/engineer/manager for a supplier of fuel pump parts to GM/Delphi and Ford/Visteon. Once there is significant play between the shaft and the bearings/bushings, the armature literally rattles around and eventually crashes into the magnets (also the pumping section is mounted on the shaft, so its close-clearance parts start rubbing against/hitting each other, depending somewhat on the type of pumping section - gerotor, turbine, moving vane, etc.). Sulfur in fuel of third world countries is a big corrosion problem for fuel pumps. Presence of silicone compounds greatly shortens brush life. The interconnecting wires can break from vibration - like if they have a nick, and the car goes over a railroad track often - vibration and the notch effect don't go well together. IIRC, brush compounds have to be specifically designed to handle large concentrations of ethanol (I may not be 100% correct on this point - been out of that field for 7 years)). I do know that sometimes metal film plastic capacitors (for EMI suppression) will be destroyed by alcohol in the fuel (alcohol molecules are so small, you can't keep them from leaching onto the capacitor and etching away the metal film. When that happens, the capacitor is no longer a capacitor - EMI problems). I'd say the shaft/bushing wear is the biggest common cause of failure (intermittent) - it's why a pump in the process of failing can often can be heard rattling. Next would be worn out brushes - also intermittent (temperature- and shock/vibration-dependent), but noiseless, but brushes are usually over-designed as far as life (length). > I do not want your speculation. I am well experienced in > pump design myself. I want facts from a study of pump > failure. Perhaps I shed some light for you with some of my comments. Certainly I do not have anywhere near exhaustive knowledge of the subject. Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x') |
Re: Repeatedly Running On A Low Tank?
ToMh wrote:
> On Jun 2, 2:12 am, "Don't Taze Me, Bro!" <N00One...@NoWhere.Com> > wrote: >> Consider filling up your tank and not letting it drop below halfway, instead >> of keeping it on low and only putting in 2 gallons here and there... >> >> http://www.foxnews.com/story/0,2933,361347,00.html >> >> Not because you could run out of gas and get stranded but because repeatedly >> running on low tends to ruin the fuel pump. > > The fuel pump is like any other fluid pump. it requires the liquid > running through it to lubricate and cool it. If you run a pump dry, > its seals can burn out fast. No. There are no dynamic seals in fuel pumps like in a typical automotive water pump. Running dry (not a credible situation in general) would not affect case seals (which are static crimped seals). > But as long as there is fluid running > through it, it will be fine. So as long as there is gas running > through the pump, it won't get damaged, but I could certainly see how > it could be damaged if you let it run out of gas... Not likely since the pumping section is at the bottom of the pump, so when you "run out of gas", there is a column of fuel extending from the pumping section of the pump (at its very bottom), thru the pump, all the way to the fuel rail and injectors. Granted that column of fuel is not moving, but it's there nonetheless. And the engine dies, and the computer turns the pump off in a matter of seconds. No real chance for significant damage from heat or lack of lubrication. > Just having a low > tank, without the pump running dry, can't possibly cause any > problems. I'll buy that. Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x') |
Re: Repeatedly Running On A Low Tank?
Retired VIP wrote:
> On Mon, 2 Jun 2008 09:26:47 -0700 (PDT), ToMh <tlhumm@hotmail.com> > wrote: > >> On Jun 2, 2:12 am, "Don't Taze Me, Bro!" <N00One...@NoWhere.Com> >> wrote: >>> Consider filling up your tank and not letting it drop below halfway, instead >>> of keeping it on low and only putting in 2 gallons here and there... >>> >>> http://www.foxnews.com/story/0,2933,361347,00.html >>> >>> Not because you could run out of gas and get stranded but because repeatedly >>> running on low tends to ruin the fuel pump. >> The fuel pump is like any other fluid pump. it requires the liquid >> running through it to lubricate and cool it. If you run a pump dry, >> its seals can burn out fast. But as long as there is fluid running >> through it, it will be fine. So as long as there is gas running >> through the pump, it won't get damaged, but I could certainly see how >> it could be damaged if you let it run out of gas. Just having a low >> tank, without the pump running dry, can't possibly cause any >> problems. > > Hmmm.....What if the pump was getting gulps of air due to the gas > sloshing around in a nearly empty tank? Is the pump pickup located in > a well or a low point in the tank? The pump will never not see fuel inside. The pumping section is at the very bottom of the pump, so the column of fuel will be "dancing" on the pumping element (think of a turbine blade). The only part (in an empty tank) filled with air will be the pickup tube. Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x') |
Re: Repeatedly Running On A Low Tank?
Daniel Who Wants to Know wrote:
> All that being said I have also personally heard the distinct sound of vapor > bubbles going through the fuel pressure regulator on a car with the engine > running. I think in some cases the pump starts sucking air through the top > of the pickup sock before the tank is completely empty but yet is still able > to supply enough pressure and volume for the engine to run. I can visualize that happening as it starts sucking bubbles of air rising into the pump thru the pickup tube. Kind of like cavitation, except air instead of nothing. Froth. Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x') |
Re: Repeatedly Running On A Low Tank?
Elle wrote:
> ...E.g. climates that have a lot moisture in the air > will tend to promote more rust in the fuel tank than if the > climate were dry... Not that much of a problem these days with sealed tanks. > From talk on the net, it does seem to me that debris > accumulating at the bottom of fuel tanks is not uncommon. > And why have a fuel filter whose changing is prescribed to > be every few years, besides, if the debris is no concern? So > too do we see reports of fuel tanks failing... FWIW, Chrysler LH cars have life-of-vehicle fuel filters, and apparently they are effective (very few posts on LH forums for fuel filter issues). > I do not think the OP's article is baloney. It's just > suggested best operating practices to minimize fuel system > problems, ISTM. Not a big deal. I do not agree that the article is not baloney, but I agree that it's not a big deal. Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x') |
Re: Repeatedly Running On A Low Tank?
"Bill Putney" <bptn@kinez.net> wrote
> I can visualize that happening as it starts sucking > bubbles of air rising into the pump thru the pickup tube. > Kind of like cavitation, except air instead of nothing. > Froth. I trust you will recall that cavitation is not bubbles filled with nothing. It is the occurrence of bubbles filled with the vapor of the liquid being moved. It is a consequence of the liquid reaching a pressure low enough to cause boiling. |
Re: Repeatedly Running On A Low Tank?
Elle wrote: snip > > I am speaking of electric fuel pumps, by the way, which are > what are used on cars with fuel injection. So anyone having > an older, carbureted car likely has a mechanical fuel pump > and will have somewhat different concerns. > Honda Civics went to electric pumps beginning with the 1980 model year but it was external right outside the tank. I have never heard of a fuel pump failure with these units. Even after setting idle for nearly 12 years, the one in my '83 works perfectly. JT |
Re: Repeatedly Running On A Low Tank?
Elle wrote:
> "Bill Putney" <bptn@kinez.net> wrote >> I can visualize that happening as it starts sucking >> bubbles of air rising into the pump thru the pickup tube. >> Kind of like cavitation, except air instead of nothing. >> Froth. > > I trust you will recall that cavitation is not bubbles > filled with nothing. It is the occurrence of bubbles filled > with the vapor of the liquid being moved. It is a > consequence of the liquid reaching a pressure low enough to > cause boiling. You are correct. Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x') |
Re: Repeatedly Running On A Low Tank?
On Mon, 02 Jun 2008 18:20:56 +0000, Daniel Who Wants to Know wrote:
>> The fuel pump is cooled by fuel. If you run on a low tank that doesn't >> cover the fuel pump, it can fail prematurely. At $190~425 for a fuel >> pump. it's probably cheaper to keep enough fuel in the tank to cool the >> pump. >> >> What did I expect from someone who changes his oil at 12,000 miles >> whether it needs it or not. >> >> Reply when you get a clue... >> >> >> > Sorry to burst your bubble hachi but the level of fuel outside the pump > means nothing. As has been mentioned before the fuel being pumped goes > directly through the motor assembly on its way from one end of the pump > to the other. But...But...Ray told me I was in danger of burning out my fuel pump in my Supra when I got it because the tank had so many holes I had to keep it below 1/4 tank. I trust what Ray says... |
Re: Repeatedly Running On A Low Tank?
On Mon, 02 Jun 2008 18:20:56 +0000, Daniel Who Wants to Know wrote:
> P.S. Why is this cross posted to about a zillion newsgroups? 'Cause the OP did to begin with. |
Re: Repeatedly Running On A Low Tank?
"Bill Putney" <bptn@kinez.net> wrote
> Elle wrote: >> ...E.g. climates that have a lot moisture in the air will >> tend to promote more rust in the fuel tank than if the >> climate were dry... > > Not that much of a problem these days with sealed tanks. Bill, the article is addressing all the saps too poor to keep their gas tanks full. You really think they're all driving cars with a model year later than about 1998, when fuel tanks were going plastic? :-) (I am just guestimating the year plastic became really popular, based on googling on the subject.) |
Re: Repeatedly Running On A Low Tank?
"Grumpy AuContraire" <Grumpy@ExtraGrumpyville.com> wrote
> Elle wrote: >> I am speaking of electric fuel pumps, by the way, which >> are what are used on cars with fuel injection. So anyone >> having an older, carbureted car likely has a mechanical >> fuel pump and will have somewhat different concerns. > > > Honda Civics went to electric pumps beginning with the > 1980 model year but it was external right outside the > tank. How'd you know this little factoid so quickly?! I believe you, just saying that's way inside information. > I have never heard of a fuel pump failure with these > units. Hm, unless you worked on Hondas of that vintage for a few years, I am not sure I can support a hypothesis that pumps of this vintage do not fail. > Even after setting idle for nearly 12 years, the one in my > '83 works perfectly. Yeabut you don't run to empty/"on fumes" (as they say), do you? Those of you attesting that the article's thesis is bunk may be right. Just saying fuel pumps do fail; more authoritative sources than Fox make the same claim the Fox article does (which is pretty darn general; look back); and those of you saying, 'Ain't never seen a fuel pump failure in my guzillion years of drivin' ' just do not run the car to empty enough or do not leave your fuel filter unchanged long enough to have a problem. |
Re: Repeatedly Running On A Low Tank?
Elle wrote:
> ...Just saying fuel pumps do fail; more authoritative > sources than Fox make the same claim the Fox article does > (which is pretty darn general; look back);.. As time goes on, I believe lees and less of what I read because much of what I see reported that I have first-hand knowledge of I know to be absolute b.s. > and those of you > saying, 'Ain't never seen a fuel pump failure in my > guzillion years of drivin' ' just do not run the car to > empty enough or do not leave your fuel filter unchanged long > enough to have a problem. My '99 Concorde just rolled over 200k miles - original fuel filter (as it is designed to last the life of the car), and I routinely run it as low as it will go before filling up on my 80 mile daily commute - almost always between 3/16 and below 'E'. Yeah - I know - a sample of one. But that is lifelong habit - have never had a fuel pump fail in over 40 years of driving/DIY'ing. Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x') |
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