Jun

iTrader: (45)

As you guys know, there is another thread going on about how our cars don't fill up all the way, it looks like the gas tank is completely full, it even spills over, yet, when you turn the car on, the needle is not even at the full mark yet.
I had taken my car to the dealership to get this fixed, they replaced the fuel pump thinking that would solve the problem. Well, it didn't, i still have the problem and it's annoying the hell out of me.
The only way i could find out if i really have 20gallons or not is to drive as much as possible to the point where the tank is almost empty....
So i've been driving around with the light on for a whole day and a half. I'd say about a good 90 miles or so. Today after leaving work, i thought, let's see how far i can make it. Well, i kept driving and driving. As I am driving, i have this feeling that the car should almost be completely dry. I passed a gas station and thought for a second, should i stop here, or can i make it to the next one. Well, not even 100yds later, the car just stalls. Called a friend, who happened to be near by, asked him if he could buy me a gallon of gas (should have thought of this previously, however, i had not planned on running out of gas!) So i filled the car with the gallon, drove to the gas station which is less than 100yds away, and got to the filling part...

gulp gulp gulp, 5 minutes later (don't know how long it took, i'm just guessing here) the pump stops at about $43 and 18.88 gallons.
Now, considering there was a gallon in the tank before that, had i not used any gas from the point my car stopped to the gas station, my tank would be capable of holding 19.88 gallons. However, i did drive a bit (less than 100yds) which means the tank is actually smaller than 19.88, since the car had to consume some gas getting to the gas station. So let's say i used 2/10ths of a gallon, that means when i started filling up, my car had already 8/10ths of a gallon, + the 18.88 = 19.68 (estimate)

Now, my question is, when Nissan says the 350z has a 20 gallon tank, do they really mean 20 gallons, or do they round up (like how they do for the displacement of the engine)?

In any case, this does not explain WHY the needle doesn't go all the way to "after" the full line, but at least i know i have a 19.6 gallon tank. My total miles driving on the previous tank was 313 miles.

The most i've gotten when i first had my car driving normal was about 350-360.


Hope this information helps to anyone who is wondering about the capacity of our tanks.

yobri

iTrader: (2)

Wow Jun... you run all sort of experiments on your car... But thanks for the report, I think it's the first of its kind so far...

Jun

iTrader: (45)

indeed it is...lol.

seriously though, i THOUGHT i had it. I should have gone with my instincts and stopped at the gas station i had just passed, the car would have probably died out right after parking it, giving me an exact reading of the situation.

oh well, this is as close as it gets, without having to sit down and wait for the car to run empty at the gas station.

BTW, nice to see you are a mod now!

fowlman01

iTrader: (1)

Thanks for the "test". Now I have an idea how far I can drive on empty.

Dr Bonz

iTrader: (1)

You have to consider the amount of gas that the tube that leads to the tank holds as well. I have actually put in slightly more than 20 gallons by "topping off" (I know that this isn't the smartest thing to do but I was curious just like Jun!)

slaponte

iTrader: (2)

This is interesting stuff, Jun. Mine used to mark correct, when full the needle would go up above the F. But recently (last few months) best I can do is to get it halfway between 3/4 and F, no matter how much I top off... So mi impression of the problem is that either the sending unit in the tank goes bad, or the needle in the cluster. I think the light is based on the nedle position (just a guess). This also throws off distance to empty, MPG calculations etc, so it is a pervasive nuisance.

I think your estimate is a close as you can get to the 20G. Remember there is fuel on the lines, and there might be some fuel left on the tank that you just can't pick up, but that is ok because it usually is "sludge" with dirt/sand, etc and you DON'T want to pick it up.

The tank or filler are not to blame. I have the same ones since day one and it used to be fine. It has to be the "measuring" system somewhere.

Jun

iTrader: (45)

that's my assumption as well.
as far as the needle throwing off the light, it doesn't. I had removed my needle previously (when i installed my gauges). There is nothing there that could trigger the light based on the position of the needle. You can remove the needle and place it as you wish, if i wanted to, i can take the needle out and on a complete tank of gas place it a hairline over the F line, sure it would look back to normal, but that still would not explain why most of the time i cannot fill up my tank completely.

How many gallons are there suppose to be in the tank when the light goes on?

burntZ

iTrader: (1)

just noted the lite on / off thing this weekend

the low fuel lite is tied to the DTE figure - as i had blasted home ( zoom zoom, to violate the trademark) i'd driven the mpg down to 20.something then the lite came on and the trip comp went to flashing DTE of 60

as i then calmed a bit the mpg increased and the lite and DTE cycled back off

so seems to be at about the 3 gallon mark

filled about 16.5 gals soon after so that nears the 20 mark also

just my $.02s worth

Jung918

I had the same problem. The dealer replaced the fuel sender unit and it works fine now. It has had only 1 fill up. Hopefully I didn't jinx myself.

Jun

iTrader: (45)

Experiment #2:

Before filling the tank, that's how many miles i had done:


Full tank:


And the needle position:


Total gas pumped: 18.003 gallons.

The DTE was flashing " - - - - ", and if i remember correctly, the last time i drove around 30 miles or so before the tank was completely empty, when the flashing started. So 30 miles/2 gallons that are still in the car = 15mpg, it sounds about average.

I guess I have to live with this minor problem of filling/not filling completely. The gas is there, we have a 20 gallon tank, it's just that sometimes it won't show completely full with the needle marker.

Oh, by the way, this time i topped the tank just to get the last drop in there (i know, it's advised not to do so), almost spilled, then i had to go in and wait for the receipt because the machine wasn't working. So the car sat for a good 5 minutes before i turned it on after filling it. First time I do this, because usually i pay with the credit card at the pump, fill it, and then drive off. So i don't know if the "waiting" was a factor or not, but it could be the possibility of the gas settling in the tank therefore giving it a better reading...

Do i have an answer to the problem? Not really, but at least you know the 20 gallon tank is there.

Hope this info is helpful to anyone.

slaponte

iTrader: (2)

Jun, your needle sits above the full line, heck, mine doesn't even get there... these 0.02mm are driving me crazy!!

This is reaching obsesion level by now... LOL

Jun

iTrader: (45)

well, if it makes you feel any better, this is the first time it does this in about 2-3 months. Usually when full, it sits about 9/10th full, sometimes even lower at 7/8th. I guess next time top it off until it spills out and no more can go in, then wonder inside the gas station for about 5 minutes, and then turn on the car.

slaponte

iTrader: (2)

Maybe you have to fill up slower to keep bubles from forming and that way you get it closer to full!!

I just wait it out and when it says 10 miles to go I know I still have 50+ in there...