Problems with gas guage
Member
Joined: 02-19-05
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From: Grand Blanc Michigan
Yep I can fill mine up, and it says 3/4 full, then if I cycle the key, it will read 7/8 full, then I can cycle it again and I am back to 3/4. Then driving sometimes it will actually go to full. So I don't know what to think of it yet. Off the lot, they said they filled it up, but it read 3/4 tank, so I just figured they didn't fill it all the way up. Sure enough though, when I filled it up for the first time, it went to 3/4, then slowly went up as I drove it to about 7/8. So I just fill it when it reads about 1/4 at the lowest. 
New Member
Joined: 12-20-04
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From: Kansas, USA
I have noticed this as well.
It's been filled up three times since I bought it, including at delivery, and it has never shown a full tank -- usually about halfway between 7/8 and full. I've also noticed that the gauge tends to "dance around quite a bit" -- it sometimes fluctuates during normal driving and there have been times when I would start it up and the gauge would be as much as 1/8 of a tank lower than when I last shut it off. I was used to going about 1 1/2 weeks between fillups with my Malibus and 1998 LeSabre, but with the Cobalt it's been 5 days each time. I was quite surprised when I went to a friend's house earlier this week with what I'm pretty sure was at least 1/8 of a tank when I shut it off, only to have it going on empty and the low fuel warning coming on when I started it up again a short time later.
It's been filled up three times since I bought it, including at delivery, and it has never shown a full tank -- usually about halfway between 7/8 and full. I've also noticed that the gauge tends to "dance around quite a bit" -- it sometimes fluctuates during normal driving and there have been times when I would start it up and the gauge would be as much as 1/8 of a tank lower than when I last shut it off. I was used to going about 1 1/2 weeks between fillups with my Malibus and 1998 LeSabre, but with the Cobalt it's been 5 days each time. I was quite surprised when I went to a friend's house earlier this week with what I'm pretty sure was at least 1/8 of a tank when I shut it off, only to have it going on empty and the low fuel warning coming on when I started it up again a short time later.
New Member
Joined: 02-25-05
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From: Whitby
That has been a problem with some domestic cars for about 3 years. The fuel volume sensor (paired with the fuel pump it is called the "fuel sender module") is very inaccurate when the volume is high (full tank). Some of the cheaper fuel senders made by Siemens and Johnson Controls have been identified as problem parts, and sometimes they blame the petroleum companies. Apparently it has something to do with the integration of Ethanol fuel and making a sensor that works with regular fuel and ethanol fuel.
New Member
Joined: 12-20-04
Posts: 143
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From: Kansas, USA
I e-mailed Chevrolet about this last night to see if anyone else has reported this problem to them. I plan to get it fixed in the not-too-distant future -- hopefully before I send in the forthcoming delivery satisfaction survey 
Junior Member
Joined: 01-13-05
Posts: 492
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From: Rockland, NY
Originally Posted by Zilla
That has been a problem with some domestic cars for about 3 years. The fuel volume sensor (paired with the fuel pump it is called the "fuel sender module") is very inaccurate when the volume is high (full tank). Some of the cheaper fuel senders made by Siemens and Johnson Controls have been identified as problem parts, and sometimes they blame the petroleum companies. Apparently it has something to do with the integration of Ethanol fuel and making a sensor that works with regular fuel and ethanol fuel.
Around April or May... they go back to a normal mix!
New Member
Joined: 02-25-05
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From: Whitby
Originally Posted by CoolCobalt_NY
I can see something like that happening.. You know the gas companies change the mixture around in the winter so the gas wont freeze!!! and the car runs like crap.....
Around April or May... they go back to a normal mix!
Around April or May... they go back to a normal mix!
You might also notice the top half of your tank lasts forever and the bottom half empties quickly... this goes back to the fuel sender being inaccurate when the volume of liquid is large. It's not as noticeable in smaller cars (smaller fuel tank) but it is very obvious on larger vehicles, especially the large SUVs.
New Member
Joined: 09-01-04
Posts: 197
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From: Bloomingburg, NY
there is a bulletin on the gauge, we've had to reprogram the computer on at least half of our cobalts before delivery... your dealers should have done it before delivery, go talk to the service dept...
New Member
Joined: 12-20-04
Posts: 143
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From: Kansas, USA
To my pleasant surprise, GM already e-mailed me back today and called me as well. I'm going to set up an appointment with the dealer tomorrow and hopefully get this fixed one week from tomorrow.
Member
Joined: 01-18-05
Posts: 292
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From: Piedmont Triad, NC
Nine times out of ten every vehicle has the same problem. Yes one can blame the pump or the "fuel sending unit" or the gas companies (or petroleum companies if you prefer) but really it's physics that is the problem more often than not.
By all means, don't be afraid to have it checked out at the dealership, it is under warranty after all.
But here's the thing, picture in your mind a perfect cube. Now at the very top of that sphere place a round cylinder the size of a pencil-holder (like the one on my desk that you can't see) into that cube, until it rests on the bottom. At the top of that cylinder attach a hose that you put gas into and have the hose coming out of the top. Take it to your local 7/11 or Quik-e-mart and fill up that cube. You'll notice that the gas pump at the gas station cuts off when it thinks the tank is full (lot's of physics here involving the limitation of flow dealing with the pump, but don't worry about that now).
So here you have this perfectly full cube. It's 100% full and there is no air in it whatsoever. Now reshape the cube to fit perfectly underneat the back seat, and reshape it again so that it has mounting points so that it doesn't slide around inside your car. You'll notice that it gets rounded corners and lumps that are on one side but not another, ridges at the top that can never get filled.
And then, to top it off, turn that tank at an angle just slightly, as if someone were sitting in the passenger seat, or the pavement isn't perfect. Now fill up the tank again, you'll see some sort of air in the top, sometimes a little, sometimes a lot.
The tank is not 100% full.
Then you could adjust the sensor to state that it is full (when it's really not) and you'll get what you have on my 86 Blazer, 300 miles on the first "half tank" and 100 miles left once it hit's 50%.
Like I said, it's just physics.
The good thing is that you only pay for the gas you use.
The bad news is that you have to pay an arm and a leg for that gas nowadays.
Villain
By all means, don't be afraid to have it checked out at the dealership, it is under warranty after all.
But here's the thing, picture in your mind a perfect cube. Now at the very top of that sphere place a round cylinder the size of a pencil-holder (like the one on my desk that you can't see) into that cube, until it rests on the bottom. At the top of that cylinder attach a hose that you put gas into and have the hose coming out of the top. Take it to your local 7/11 or Quik-e-mart and fill up that cube. You'll notice that the gas pump at the gas station cuts off when it thinks the tank is full (lot's of physics here involving the limitation of flow dealing with the pump, but don't worry about that now).
So here you have this perfectly full cube. It's 100% full and there is no air in it whatsoever. Now reshape the cube to fit perfectly underneat the back seat, and reshape it again so that it has mounting points so that it doesn't slide around inside your car. You'll notice that it gets rounded corners and lumps that are on one side but not another, ridges at the top that can never get filled.
And then, to top it off, turn that tank at an angle just slightly, as if someone were sitting in the passenger seat, or the pavement isn't perfect. Now fill up the tank again, you'll see some sort of air in the top, sometimes a little, sometimes a lot.
The tank is not 100% full.
Then you could adjust the sensor to state that it is full (when it's really not) and you'll get what you have on my 86 Blazer, 300 miles on the first "half tank" and 100 miles left once it hit's 50%.
Like I said, it's just physics.
The good thing is that you only pay for the gas you use.
The bad news is that you have to pay an arm and a leg for that gas nowadays.
Villain
Senior Member
Joined: 10-15-04
Posts: 701
Likes: 0
From: Calgary, AB
Originally Posted by BlueVillain
Nine times out of ten every vehicle has the same problem. Yes one can blame the pump or the "fuel sending unit" or the gas companies (or petroleum companies if you prefer) but really it's physics that is the problem more often than not.
By all means, don't be afraid to have it checked out at the dealership, it is under warranty after all.
But here's the thing, picture in your mind a perfect cube. Now at the very top of that sphere place a round cylinder the size of a pencil-holder (like the one on my desk that you can't see) into that cube, until it rests on the bottom. At the top of that cylinder attach a hose that you put gas into and have the hose coming out of the top. Take it to your local 7/11 or Quik-e-mart and fill up that cube. You'll notice that the gas pump at the gas station cuts off when it thinks the tank is full (lot's of physics here involving the limitation of flow dealing with the pump, but don't worry about that now).
So here you have this perfectly full cube. It's 100% full and there is no air in it whatsoever. Now reshape the cube to fit perfectly underneat the back seat, and reshape it again so that it has mounting points so that it doesn't slide around inside your car. You'll notice that it gets rounded corners and lumps that are on one side but not another, ridges at the top that can never get filled.
And then, to top it off, turn that tank at an angle just slightly, as if someone were sitting in the passenger seat, or the pavement isn't perfect. Now fill up the tank again, you'll see some sort of air in the top, sometimes a little, sometimes a lot.
The tank is not 100% full.
Then you could adjust the sensor to state that it is full (when it's really not) and you'll get what you have on my 86 Blazer, 300 miles on the first "half tank" and 100 miles left once it hit's 50%.
Like I said, it's just physics.
The good thing is that you only pay for the gas you use.
The bad news is that you have to pay an arm and a leg for that gas nowadays.
Villain
By all means, don't be afraid to have it checked out at the dealership, it is under warranty after all.
But here's the thing, picture in your mind a perfect cube. Now at the very top of that sphere place a round cylinder the size of a pencil-holder (like the one on my desk that you can't see) into that cube, until it rests on the bottom. At the top of that cylinder attach a hose that you put gas into and have the hose coming out of the top. Take it to your local 7/11 or Quik-e-mart and fill up that cube. You'll notice that the gas pump at the gas station cuts off when it thinks the tank is full (lot's of physics here involving the limitation of flow dealing with the pump, but don't worry about that now).
So here you have this perfectly full cube. It's 100% full and there is no air in it whatsoever. Now reshape the cube to fit perfectly underneat the back seat, and reshape it again so that it has mounting points so that it doesn't slide around inside your car. You'll notice that it gets rounded corners and lumps that are on one side but not another, ridges at the top that can never get filled.
And then, to top it off, turn that tank at an angle just slightly, as if someone were sitting in the passenger seat, or the pavement isn't perfect. Now fill up the tank again, you'll see some sort of air in the top, sometimes a little, sometimes a lot.
The tank is not 100% full.
Then you could adjust the sensor to state that it is full (when it's really not) and you'll get what you have on my 86 Blazer, 300 miles on the first "half tank" and 100 miles left once it hit's 50%.
Like I said, it's just physics.
The good thing is that you only pay for the gas you use.
The bad news is that you have to pay an arm and a leg for that gas nowadays.
Villain
Junior Member
Joined: 01-13-05
Posts: 492
Likes: 0
From: Rockland, NY
So.....If you Reprogram the computer with it be fixed... or not??? Thats all I care about...
But I do see what you are saying Villian.....!!!! Like I said, new car, it should all work correctly, if not the first or the second time, well the third time better be the last time..
I also understand that new cars on the market always have gliches in them... ( I think I have posted something like this somewhere)
The first half off the line always have problems most of the time.. The second half is where they made all the correction.... Usually, from what I know, that's how it works..
ANyway... I'll shut up now..
But I do see what you are saying Villian.....!!!! Like I said, new car, it should all work correctly, if not the first or the second time, well the third time better be the last time..
I also understand that new cars on the market always have gliches in them... ( I think I have posted something like this somewhere)
The first half off the line always have problems most of the time.. The second half is where they made all the correction.... Usually, from what I know, that's how it works..
ANyway... I'll shut up now..
Member
Joined: 01-18-05
Posts: 292
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From: Piedmont Triad, NC
Originally Posted by CoolCobalt_NY
So.....If you Reprogram the computer with it be fixed... or not??? Thats all I care about...
But I do see what you are saying Villian.....!!!! Like I said, new car, it should all work correctly, if not the first or the second time, well the third time better be the last time..
I also understand that new cars on the market always have gliches in them... ( I think I have posted something like this somewhere)
The first half off the line always have problems most of the time.. The second half is where they made all the correction.... Usually, from what I know, that's how it works..
ANyway... I'll shut up now..
But I do see what you are saying Villian.....!!!! Like I said, new car, it should all work correctly, if not the first or the second time, well the third time better be the last time..
I also understand that new cars on the market always have gliches in them... ( I think I have posted something like this somewhere)
The first half off the line always have problems most of the time.. The second half is where they made all the correction.... Usually, from what I know, that's how it works..
ANyway... I'll shut up now..
I guess it just shows that you're a "half full" kinda guy then. Just too bad none of us can be "100% full"
Villain
Junior Member
Joined: 01-13-05
Posts: 492
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From: Rockland, NY
Half Full
No not at all... Just trying to find out whats up that's all... Looking at ALL THE INFO on it...
Like you said, the techs at the dealership should be able to give me and you guys the final word...
ANyway... I still have not heard anything thing about my car.. Maybe tomorrow since tonight all the dealerships get a fax or something...
Maybe I'll know more tomorrow!
Like you said, the techs at the dealership should be able to give me and you guys the final word...
ANyway... I still have not heard anything thing about my car.. Maybe tomorrow since tonight all the dealerships get a fax or something...
Maybe I'll know more tomorrow!
Moderator Alumni
Joined: 08-26-04
Posts: 4,944
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From: RTP, NC
Originally Posted by b-spot
That may just be the most long winded version of "the gas tank is an irregular shape" that I've ever read.
Member
Joined: 01-18-05
Posts: 292
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From: Piedmont Triad, NC
Originally Posted by PenguinPIE
say....theres this problem with the fuel gauge......is it gonna affect the accuracy of the fuel range? (in the DIC)
For those of you who who weren't around when we did this every time:
Fill up your tank all the way, and reset your trip-o-meter.
Drive normally for a couple of days.
Fill up your tank again.
How ever much gas you used, divide it into the number of miles you went on that tank.
See if that comes close to what your DIC says.
Villain
Thread Starter
New Member
Joined: 02-26-05
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From: Hamilton
Got mine fixed today
Took my Cobalt to the dealer today. Arrived about 7:30 - left 9:30. They verified the "concern". Reprogrammed PCM per bulletin #05-08-49-002A. Everything is great now. Tank reads full. We'll see what happens when it gets closer to empty.