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Car Forum / Nissan / Nissan Cars / November 2005Cheating gas station? True tank capacity?
Hi, I'm trying to get some info before I get mad :) I've got a 2004 Sentra 1.8s and filled up the tank yesterday. I went about 1.5 miles from when the fuel light came on to pulling into the gas station. I was able to put in 13.21 gallons. Does the light come on that late or can the tank hold more that the 13.5 gallons listed? This is one of the very few times I've run the tank low enough for the light to come on. I used a gas station that isn't very common in these parts and wonder if they might have played with the pump so a gallon isn't a gallon. Anyone ever go after a cheating gas station and win? Thanks a bunch in advance. On 11/1/05 11:44 AM, in article 1130867076.023893.247280@g49g2000cwa.googlegroups.com, > Hi, > [quoted text clipped - 13 lines] > > Thanks a bunch in advance. If you topped it off, the hoses from the filler cap down to the tank usually hold about a gallon in addition to what is in the tank itself. The warning lights are pretty paranoiac and usually come on about 3 gallons from empty when they are working correctly. The light on my '96 I30 started coming on later and later last fall and now it never comes on at all (as we found out the hard way). You probably should watch the gauge and not wait for the light next time. > On 11/1/05 11:44 AM, in article > 1130867076.023893.247280@g49g2000cwa.googlegroups.com, [quoted text clipped - 25 lines] > found out the hard way). You probably should watch the gauge and not wait > for the light next time. It's been said that topping off damages the warning light mechanism. Given my experience that may be true:) CD > It's been said that topping off damages the warning light mechanism. > Given my experience that may be true:) How can it be true ? How come this extra gallon do any harm ? Sounds booooogus. >> It's been said that topping off damages the warning light mechanism. >> Given my experience that may be true:) > > How can it be true ? How come this extra gallon do any harm ? > Sounds booooogus. Well, I replaced the feul pump in my sentra and attached to it I found a mechanism which I beleive is the low feul warning mechanism. It seems to work just like the the plunger in a toilet bowl. This ball with air in it floats above the gas. That floater is tied to a somewhat flimsy metal rod which attaches to some sort of circuit. The circuit apparently measures the swing of the rod. If you fill up with too much gas the "floater" may be pushed too far, bending the flimsy rod a little, and thus fmaking the mechanism lose its accuracy at detecting low feul levels. That's what I saw. From my experience, I tend to over fill alot, and slowly I noticed my previous Altima lose accuracy in detecting low feul levels. CD > Well, I replaced the feul pump in my sentra and attached to it I found a > mechanism which I beleive is the low feul warning mechanism. It seems to [quoted text clipped - 4 lines] > "floater" may be pushed too far, bending the flimsy rod a little, and > thus fmaking the mechanism lose its accuracy at detecting low feul levels. What you saw is the fuel gauge sensor, sometimes called a "sender unit". The warning light is usually made as an addition to the fuel gauge: when the electric current flowing through the variable resistor in the sending unit and the gauge is large enough for the gauge to show near "empty" the warning light will also go on. Notice that when the tank is already full, the fuel is up to the ceiling of the tank and the float does not have any room to go anywhere so it stays submerged in fuel. It will not move until the fuel level drops... You may have noticed how your gauge tends to stay on full for quite a while after filling up. So I am pretty sure filling the hoses from the filling cap down when you top-off would not change a thing... > That's what I saw. From my experience, I tend to over fill alot, and > slowly I noticed my previous Altima lose accuracy in detecting low feul > levels. Your observation may be true, but the correlation between topping off and diminishing fuel measuring accuracy totaly not existent... What you probably see is the variable resistor in the sending unit getting old and dirty, not conducting electric current like it used to when it was brand new. That is all. I would not blame topping off. >> Well, I replaced the feul pump in my sentra and attached to it I found >> a mechanism which I beleive is the low feul warning mechanism. It [quoted text clipped - 28 lines] > getting old and dirty, not conducting electric current like it used to > when it was brand new. That is all. I would not blame topping off. Fair enough. I'll continue to top off with confidence then! CD Topping off is generally not a good idea environmentally. Much of the extra fuel just evaporates. >>> Well, I replaced the feul pump in my sentra and attached to it I found >>> a mechanism which I beleive is the low feul warning mechanism. It [quoted text clipped - 26 lines] >Fair enough. I'll continue to top off with confidence then! >CD Sorry, I didn't mean filling the tank often is bad but putting the extra gas after the gas pump has already stopped pumping. >Topping off is generally not a good idea environmentally. Much of the >extra fuel just evaporates. [quoted text clipped - 29 lines] >>Fair enough. I'll continue to top off with confidence then! >>CD On 11/23/2005 10:44 PM US(ET), ??? took fingers to keyboard, and typed the following: > Topping off is generally not a good idea environmentally. Much of the > extra fuel just evaporates. > Today's gas caps are not vented as they were in the past. That's why the Check Engine light can come on when the caps are not tight. Even if they were vented, are you saying that the gas in a few square inches of surface area, like in the filler neck, is likely to evaporate more than if the surface area of the gas was as wide and long as the gas tank? That goes against what little I know of physics. > >> [quoted text clipped - 35 lines] >> CD >>  SignatureBill > On 11/23/2005 10:44 PM US(ET), ??? took fingers to keyboard, and typed > the following: [quoted text clipped - 59 lines] >>> CD >>> There is probably a scavenger system to reduce emissions which absorbs the fuel vapour from the top of the tank when under positive pressure, where it is stored in a cannister of absorbent material (carbon?). It is released under a partial vacuum situation. Perhaps when the filler throat is full it upsets things? Is it possible that when the On 11/1/05 3:19 PM, in article hZQ9f.4976$ex4.2044@fe08.lga, "Codifus" <codifus@optonline.net> wrote: >>> It's been said that topping off damages the warning light mechanism. >>> Given my experience that may be true:) [quoted text clipped - 10 lines] > "floater" may be pushed too far, bending the flimsy rod a little, and > thus fmaking the mechanism lose its accuracy at detecting low feul levels. That float is the gauge mechanism. It should not bend no matter what you put in the tank (except maybe if you filled it with lead balls). > That's what I saw. From my experience, I tend to over fill alot, and > slowly I noticed my previous Altima lose accuracy in detecting low feul > levels. > > CD On 11/1/05 2:52 PM, in article dk80bk.bc.0@poczta.onet.pl, "Pszemol" >> It's been said that topping off damages the warning light mechanism. >> Given my experience that may be true:) > > How can it be true ? How come this extra gallon do any harm ? > Sounds booooogus. I also don't see how this can be true. The warning light is triggered by the same mechanism that reads the tank float. when its full, its full. The float would be at its limit. The only thing I have heard recently about topping off is fear that raw gas might get into the charcoal canister. > It's been said that topping off damages the warning light mechanism. > Given my experience that may be true:) > > CD I always fill to the brim. I estimate I did this about 250 times to my old Primera to get to the 115,000 miles where I reckoned it wasn't worth fixing (leaky radiator, [original] clutch on the way out) and it always worked fine. BTW, someone else thought it was worth fixing, it's still on the road. Andy >> On 11/1/05 11:44 AM, in article >> 1130867076.023893.247280@g49g2000cwa.googlegroups.com, [quoted text clipped - 35 lines] > > CD Topping off has no negative impact whatsoever. Continually letting the tank go below 1/4 does have a negative impact...the fuel pump must work much harder at low fuel levels to develop sufficient vacuum to keep gas flowing to the engine. In addition, letting the tank go to nearly empty causes sediments that would normally be at the bottom of the tank to be introduced into the fuel system, clogging filters and making the pump work harder. best advice is to never let the fuel tank get below 1/4. Bobby > In addition, letting the tank go to nearly empty causes sediments > that would normally be at the bottom of the tank to be introduced > into the fuel system, clogging filters and making the pump work harder. Have you guys ever cut the tank open to see these "sediments"? I have heard about these sediments but I have never had a chance to see them... ;-) > best advice is to never let the fuel tank get below 1/4. I would guess the fuel is bouncing left and right there on every turn stirring "sediments" from the bottom no matter if it is 1/4 or 1/16 full. >> In addition, letting the tank go to nearly empty causes sediments >> that would normally be at the bottom of the tank to be introduced into [quoted text clipped - 8 lines] > I would guess the fuel is bouncing left and right there on every turn > stirring "sediments" from the bottom no matter if it is 1/4 or 1/16 full. The detergent that is included in most modern gasolines keeps the sediment from staying suspended in the gasoline for any length of time (in addition to helping keep the lines clean). In most driving situations, the sediments are not a problem. only when the gas gets very low and they have nowhere else to go do they get sucked into the system. Bobby > The detergent that is included in most modern gasolines keeps the sediment > from staying suspended in the gasoline for any length of time (in addition > to helping keep the lines clean). In most driving situations, the sediments > are not a problem. only when the gas gets very low and they have nowhere > else to go do they get sucked into the system. Interesting stuff, where did you read about it ? I would like to know more. >>>In addition, letting the tank go to nearly empty causes sediments >>>that would normally be at the bottom of the tank to be introduced into [quoted text clipped - 16 lines] > > Bobby How bad a problem can this be? The feul pump has a strainer at the receiving end and feul filter at the injector end. It looks like the system is well protected. Just wondering. CD On 11/2/05 9:20 AM, in article PO4af.38699$rE2.32027@fe10.lga, "Codifus" <codifus@optonline.net> wrote: >>>> In addition, letting the tank go to nearly empty causes sediments >>>> that would normally be at the bottom of the tank to be introduced into [quoted text clipped - 24 lines] > > CD I always run them down to within 1 or 2 gallons remaining. I have only experienced sediment problems once (driving for 40 years now) and then it was with a diesel Oldsmobile. The filter screen at the inlet in the tank clogged and the car wouldn't run because nothing got through. I think you are correct that the filters will prevent it from harming anything. >>>>In addition, letting the tank go to nearly empty causes sediments >>>>that would normally be at the bottom of the tank to be introduced into [quoted text clipped - 24 lines] > > CD Please re-read my post. The problem is worst when letting the tank become nearly empty. If the tank is kept above being "nearly empty", then the sediments rarely if ever cause any problems. When changing defective senders, or replacing damaged tanks, I have seen instances where there were alarming amounts of rust, ketones and varnish at the bottom of the tank. If you read my post, you'll see I stated that under normal driving (i.e. never letting the tank approach empty", it's not a problem. I was responding to someone who claims to always let their tank get nearly empty, which causes the fuel pump to work harder and increases the chances of damage to the fuel system from the accumulated sediments. If you have ever looked at a gas tank, most have little valley like depressions stamped into the metal. This is for the accumulation of the sediments. > Topping off has no negative impact whatsoever. Continually letting the tank > go below 1/4 does have a negative impact...the fuel pump must work much [quoted text clipped - 5 lines] > > Bobby Well I always did that for the 100k as well... I think that's a myth TBH. Andy >> Topping off has no negative impact whatsoever. Continually letting the >> tank go below 1/4 does have a negative impact...the fuel pump must work [quoted text clipped - 9 lines] > > Andy Believe what you will...it's a free country. Allowing a tank to approach empty stresses the fuel pump unnecessarily, period. No need to make the system work harder than it has to. Besides, why risk running out of gas? Bobby >>Well I always did that for the 100k as well... I think that's a myth TBH. >> [quoted text clipped - 5 lines] > > Bobby They say this is a free country too - but that's another matter. I can't believe the extra head of fuel in the tank - it's what, a foot high? - can make any difference. And I knew that I had another 50 miles at least in the tank, I wasn't going to run out (petrol stations are never that far apart, it's not like the gas stations in the middle of Nevada). I also object to visiting the petrol station too often, it's off my route and I reckon I waste 5 minutes every time I go there. This minutes add up... Jason might have a point about the cooling. That's far more likely than the actual pressure difference. Still - as neither of us have good data (as in, stats from hundreds of cars) lets just agree to differ. Andy >> Topping off has no negative impact whatsoever. Continually letting the tank >> go below 1/4 does have a negative impact...the fuel pump must work much [quoted text clipped - 5 lines] > > Well I always did that for the 100k as well... I think that's a myth TBH. Same here. I always refuel when my warning indicator is on for a while. And I always top it off to the cap - I just hate wasting my time on taking fuel. Never had any trouble with the fuel pump in both of my vehicles... It could be some of vehicles are better in their pumps and some worse. I have toyota camry '95 purchased in 98 at 47kmiles - now it has 192k. I also have nissan sentra '94 purchased in 02 at 87kmiles - now it has 140k. Had two cars before 1998 in Europe, with significant millage on them too. Never had problems with fuel pumps, fuel injectors nor gunk in the fuel tank. Sounds like the myth based on the anegdotal evidence. >>> Topping off has no negative impact whatsoever. Continually letting >>> the tank go below 1/4 does have a negative impact...the fuel pump [quoted text clipped - 20 lines] > tank. > Sounds like the myth based on the anegdotal evidence. I would tend to agree. I've also noticed that feul pumps have gotten much smaller and more powerful. The feul pump in the 96 Altima is twice the size of the feul pump in the 98 Altima yet they both have drive same engine, more powerfull in the 98 version of course. CD >>>> Topping off has no negative impact whatsoever. Continually letting the >>>> tank go below 1/4 does have a negative impact...the fuel pump must work [quoted text clipped - 26 lines] > > CD The issue is only on vehicles that have the pump located in the tank. It has nothing to do with working harder, it has to do with heat dissipation. Most in-tank fuel pumps are designed to use the fuel surrounding the pump to cool it down, as opposed to ones mounted outside the tank which uses the fuel flowing through the pump to cool it. The number one killer of any electric motor is overheating. >>>>>Topping off has no negative impact whatsoever. Continually letting the >>>>>tank go below 1/4 does have a negative impact...the fuel pump must work [quoted text clipped - 34 lines] > fuel flowing through the pump to cool it. The number one killer of any > electric motor is overheating. Aren't all modern feul pumps inside the tank? I was under the impression that that was part of the evolution of the technology. External feul pumps are from older cars, like drum brakes, carbureutors, etc. I can understand and beleive the heat dissipation part, but it seems that feul pumps have become so bullet proof that they can withstand years and years of low-feul situations without going bust. I have replaced 2 feul pumps in 2 cars, and I'm sure their failure was due to severe lack of maintenance on the previous owner's part. My 99 Sentra felt like it had the original Nissan feul filter when the car was new, and I bought it used at 94K miles! The car had absolutely no power on the highway. I replaced the feul filter and a significant amout of power came back. Replacing the feul pump, it hadn't died but I suspected that it was dying due to un-even strange accelerative behavior, got rid of the last of those strange quirks. CD > This is one of the very few times I've run the tank low enough > for the light to come on. I used a gas station that isn't very common > in these parts and wonder if they might have played with the pump so a > gallon isn't a gallon. Anyone ever go after a cheating gas station and > win? First, *you* will have to PROVE it. And this is not easy if your only measuring tool is "estimated tank capacity" listed in your car User Manual... If I would suspect a site to do this kind of tricks I would buy red, 5 gallons gas tank, calibrate it carefully with water first and some good measuring cups, and then go to the site with previously calibrated, marked gas container and check my suspicion before I jump the gun... You cannot tell a thing based on the capacity of your tank and the warning light going on/off as the measuring device... Let's not be paranoic... :-) Pumps are calibrated by WEIGHTS & MEASURES and their volumetric meters are sealed. Breaking the seal and playing with the meter would risk serious penalties and going to jail. And depending on the town/city you need to periodically retest the pumps to get new certificates - it is not that easy to stesl the gas. It's too awesome -- 1mmg6cN |
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