Fuel gauge way off

JackDodge · 10-20-2005, 01:21 PM

Two weekends ago, I went in to the dealership for an oil change. A few days later, the gauge tells me I'm almost out of gas even though the trip indicated that I had at least a couple of hundred miles before that was actually the case. I fill it up and it takes only 7 gallons. After about one hundred miles, the fuel gauge shows around half full. I take it to the dealership. They look it over and say that they can't find anything wrong but when I have more time to bring it back and they'd reinitialize the fuel system. A few days later, The low fuel alarm goes off even sooner than the last time. I keep going and at 416 miles, the car just plain shuts down and I'm stranded on the road. After getting towed in to the dealership, they say that if the car says it's low on fuel, then it's low on fuel. I say that's not possible because I've only driven 416 miles and I get at least 52 mpg average so how can I be out of gas? They checked for a couple more hours before deciding that they should drive me home and call me when they're done. Around 6:00 PM, they call and say that they just don't know what the problem is, that Toyota has never heard of this problem before and that they are opening a new case file on it. It sounds as if they had already figured out that the car wasn't, in fact, out of gas and that it wasn't the bladder. They surmised that it may be the attitude control or the display itself. So, I'm driving around in a rental Camry, courtesy of the dealership who says that it's 99% sure that they'll have my car back to me today but it's disconcerting that they simply don't know what the problem is and my car has turned in to a classroom project to learn from. Anyone out there have any ideas on this? Maybe the dealership could use the help eh? Anyway, I'd sure like to know what the heck is going on.

galaxee · 10-20-2005, 02:17 PM

have they tried resetting the inclinometer? if not, maybe suggest it. it can cause some strange fuel gauge action.

JackDodge · 10-20-2005, 03:55 PM

Yes, they did that yesterday. They've been testing my car for two days and haven't been able to find anything wrong with it. There's another Prius right next to it in the bay and they've duplicated the tests on that one and the results are the same for both cars. It just doesn't make any sense. They verified that it was, in fact, dead empty when it came in on the flatbed tow truck too so at this point, no one here can figure it out. They also say that the bladder contracts in the winter so my problem could get worse.

Maytrix · 10-20-2005, 04:11 PM

I think it just goes to show that it pays to fill up when low. Why try to calculate when you have a nice display that should tell you when it's time. At any rate, it certainly seems like it was accurate in this case, since they did determine the tank was empty.

In addition, I'm not sure I understand your numbers..

1. Car says you need to fill up - you feel you have 200 miles to go still (big assumption since bladder and fillups from pumps can cause 3 gallon variances at times)
2. You add 7 gallons
3. At 416 miles, you run out of gas.

I'm not sure I see that there's a problem at all. Here's Why

1. Maybe with your last fill up, you didn't put in quite as much fuel, so the tank wasn't really full, so you didn't really have 200 more miles to go.
2. 7 gallons - would seem to indicate 3 gallons in tank, but that's not always the case
3. Assume 50mpg. That would be 350 miles on the 7 gallons you put in. We at least know the tank had that much in it. You went past this by 66 miles. At least another gallon.

So - Things seem to add up in my opinion. If you are so determined to fill up based on the odometer vs the gas gauge, keep a log of fill ups so you know how much went in each time and how many mpg you were really getting.

The one missing number from the above equation is how many gallons did you put in at the previous fill up? Either way, this doesn't seem that far off.

JackDodge · 10-20-2005, 04:30 PM

I'm starting to think along that line, too, Maytrix. The first thing that made me think that something was wrong was that normally when the low fuel indicator beep goes off, and I fill up, it takes around ten gallons. Now it takes seven? That seems pretty far off.

The second thing, after I fill up and only about a hundred miles in to the tankfull, The fuel gauge reads half full. That's a problem. Both of these things made me worry and caused the dealership to do all of their tests. Something is definitely wrong but I haven't figured it out yet. Maybe they gas stations around here are using their winter mix already. Maybe I got ethanol but I doubt it since I always use Mobil. In any case, why would the car show half full so soon?

galaxee · 10-20-2005, 05:35 PM

OHHHH...

i didn't notice you were in MICHIGAN. it's starting to get cold again in the midwest isn't it? (i'm a WI native, should have thought of that)

yes, this will really affect your car's fuel bladder and you may have a hard time putting much gas in at once. here in nc is's still in the 80s (sigh) and i have a hard time getting more than 9 gallons in. i can see 7 being a pretty reasonable number considering the temp difference.

seasidetraveler · 10-20-2005, 06:02 PM

My fuel gauge is terrible- I can go almost 150 miles before 1 bar goes down, but after that, they start falling like bricks- I really don't like that- but I deal- I have just learned to get gas at half tank.

JackDodge · 10-21-2005, 11:13 AM

They reset the fuel gauge, too, so we'll see what happens. They put a couple of gallons or so in the tank so I don't quite know how much was left when I filled it up this morning but it took a little over 7 gallons. Just another aspect of the Prius that is very different from other cars. Thanks for the input.

Marlin · 10-21-2005, 12:01 PM

Quote:

Originally posted by remaxmanager@Oct 20 2005, 06:02 PM
My fuel gauge is terrible- I can go almost 150 miles before 1 bar goes down, but after that, they start falling like bricks- I really don't like that- but I deal- I have just learned to get gas at half tank.

[snapback]143452[/snapback]

You have probably never owned a car that didn't behave this way. However you probably never noticed or cared. The only reason you notice it now is that you are constantly watching your MPG, miles driven, and you fuel gauge. This is something you probably never did on you previous car.

When I filled my old explorer, the fuel guage needle would peg on the stop pin well pas the "F", and would stay there for many miles before it started to drop. When I looked at the fuel gauge, I only cared about whether it was above 1/4 or below. If it was below 1/4, then I got gas, if it was above, then I didn't. I didn't track milage and I didn't have realtime MPG updates, so I wasn't sitting there saying "I know I've gotten XX mpg this tank and I've gone yyy miles, therefore I should be at 1/2 a tank, not 1/3".

You also have to consider that gas tanks are not perfectly square. Look at this one from an 87 Corolla:

The only way to get a perfectly linear gas guage out of that is to use considerably more complex electronics than is warrented for something as mundane as a gas guage.

Cyndrax · 10-21-2005, 12:15 PM

Quote:

Originally posted by Marlin@Oct 21 2005, 11:01 AM
The only way to get a perfectly linear gas guage out of that is to use considerably more complex electronics than is warrented for something as mundane as a gas guage.

[snapback]143703[/snapback]

It would seem to me that with computer power as cheap as it is these days, it would be possible for a car to do this reliably at minimal expense.

10-20-2005, 01:21 PM	#1
JackDodge Gold Member Join Date: Sep 2005 Location: Bloomfield Hills, MI Posts: 2,375 My Car: Other Hybrid Model: Package: N/A Thanks: 2 Thanked 2 Times in 2 Posts Friends: 0	Two weekends ago, I went in to the dealership for an oil change. A few days later, the gauge tells me I'm almost out of gas even though the trip indicated that I had at least a couple of hundred miles before that was actually the case. I fill it up and it takes only 7 gallons. After about one hundred miles, the fuel gauge shows around half full. I take it to the dealership. They look it over and say that they can't find anything wrong but when I have more time to bring it back and they'd reinitialize the fuel system. A few days later, The low fuel alarm goes off even sooner than the last time. I keep going and at 416 miles, the car just plain shuts down and I'm stranded on the road. After getting towed in to the dealership, they say that if the car says it's low on fuel, then it's low on fuel. I say that's not possible because I've only driven 416 miles and I get at least 52 mpg average so how can I be out of gas? They checked for a couple more hours before deciding that they should drive me home and call me when they're done. Around 6:00 PM, they call and say that they just don't know what the problem is, that Toyota has never heard of this problem before and that they are opening a new case file on it. It sounds as if they had already figured out that the car wasn't, in fact, out of gas and that it wasn't the bladder. They surmised that it may be the attitude control or the display itself. So, I'm driving around in a rental Camry, courtesy of the dealership who says that it's 99% sure that they'll have my car back to me today but it's disconcerting that they simply don't know what the problem is and my car has turned in to a classroom project to learn from. Anyone out there have any ideas on this? Maybe the dealership could use the help eh? Anyway, I'd sure like to know what the heck is going on. __________________ "Isolation exists only in isolation. Once shared, it evaporates" - Dr. Breuer from the movie "When Nietzsche Wept"

10-20-2005, 04:11 PM	#4
Maytrix Senior Member Join Date: Aug 2005 Location: Marlborough, Mass Posts: 734 My Car: 2005 Prius Model: Package: #6 Thanks: 0 Thanked 1 Time in 1 Post Friends: 0	I think it just goes to show that it pays to fill up when low. Why try to calculate when you have a nice display that should tell you when it's time. At any rate, it certainly seems like it was accurate in this case, since they did determine the tank was empty. In addition, I'm not sure I understand your numbers.. 1. Car says you need to fill up - you feel you have 200 miles to go still (big assumption since bladder and fillups from pumps can cause 3 gallon variances at times) 2. You add 7 gallons 3. At 416 miles, you run out of gas. I'm not sure I see that there's a problem at all. Here's Why 1. Maybe with your last fill up, you didn't put in quite as much fuel, so the tank wasn't really full, so you didn't really have 200 more miles to go. 2. 7 gallons - would seem to indicate 3 gallons in tank, but that's not always the case 3. Assume 50mpg. That would be 350 miles on the 7 gallons you put in. We at least know the tank had that much in it. You went past this by 66 miles. At least another gallon. So - Things seem to add up in my opinion. If you are so determined to fill up based on the odometer vs the gas gauge, keep a log of fill ups so you know how much went in each time and how many mpg you were really getting. The one missing number from the above equation is how many gallons did you put in at the previous fill up? Either way, this doesn't seem that far off. __________________ __________________________________________________ 2005 Salsa Red Pkg #6. Acquired Sept 1st 2005. 31404 miles as of 9-13-06

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10-20-2005, 02:17 PM	#2
galaxee resident lab rat Join Date: Mar 2005 Location: boilermaker territory Posts: 9,676 My Car: 2005 Prius Model: N/A Package: #5 Thanks: 0 Thanked 94 Times in 37 Posts Friends: 26	have they tried resetting the inclinometer? if not, maybe suggest it. it can cause some strange fuel gauge action.

10-20-2005, 03:55 PM	#3
JackDodge Gold Member Join Date: Sep 2005 Location: Bloomfield Hills, MI Posts: 2,375 My Car: Other Hybrid Model: Package: N/A Thanks: 2 Thanked 2 Times in 2 Posts Friends: 0	Yes, they did that yesterday. They've been testing my car for two days and haven't been able to find anything wrong with it. There's another Prius right next to it in the bay and they've duplicated the tests on that one and the results are the same for both cars. It just doesn't make any sense. They verified that it was, in fact, dead empty when it came in on the flatbed tow truck too so at this point, no one here can figure it out. They also say that the bladder contracts in the winter so my problem could get worse.

10-20-2005, 04:30 PM	#5
JackDodge Gold Member Join Date: Sep 2005 Location: Bloomfield Hills, MI Posts: 2,375 My Car: Other Hybrid Model: Package: N/A Thanks: 2 Thanked 2 Times in 2 Posts Friends: 0	I'm starting to think along that line, too, Maytrix. The first thing that made me think that something was wrong was that normally when the low fuel indicator beep goes off, and I fill up, it takes around ten gallons. Now it takes seven? That seems pretty far off. The second thing, after I fill up and only about a hundred miles in to the tankfull, The fuel gauge reads half full. That's a problem. Both of these things made me worry and caused the dealership to do all of their tests. Something is definitely wrong but I haven't figured it out yet. Maybe they gas stations around here are using their winter mix already. Maybe I got ethanol but I doubt it since I always use Mobil. In any case, why would the car show half full so soon?

10-20-2005, 05:35 PM	#6
galaxee resident lab rat Join Date: Mar 2005 Location: boilermaker territory Posts: 9,676 My Car: 2005 Prius Model: N/A Package: #5 Thanks: 0 Thanked 94 Times in 37 Posts Friends: 26	OHHHH... i didn't notice you were in MICHIGAN. it's starting to get cold again in the midwest isn't it? (i'm a WI native, should have thought of that) yes, this will really affect your car's fuel bladder and you may have a hard time putting much gas in at once. here in nc is's still in the 80s (sigh) and i have a hard time getting more than 9 gallons in. i can see 7 being a pretty reasonable number considering the temp difference.

10-20-2005, 06:02 PM	#7
seasidetraveler Senior Member Join Date: Apr 2005 Location: CA Posts: 623 My Car: 2006 Prius Model: N/A Package: #6 Thanks: 0 Thanked 1 Time in 1 Post Friends: 0	My fuel gauge is terrible- I can go almost 150 miles before 1 bar goes down, but after that, they start falling like bricks- I really don't like that- but I deal- I have just learned to get gas at half tank.

10-21-2005, 11:13 AM	#8
JackDodge Gold Member Join Date: Sep 2005 Location: Bloomfield Hills, MI Posts: 2,375 My Car: Other Hybrid Model: Package: N/A Thanks: 2 Thanked 2 Times in 2 Posts Friends: 0	They reset the fuel gauge, too, so we'll see what happens. They put a couple of gallons or so in the tank so I don't quite know how much was left when I filled it up this morning but it took a little over 7 gallons. Just another aspect of the Prius that is very different from other cars. Thanks for the input.