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Fuel Gauge Keeps Moving


djrobnyc

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I just recently bought a 95 vert, 3.4L. The fuel gauge seems to "float." When accelerating it goes up, when idling it moves back down. I can't seem to get it to sit still. Anyone have this issue? Could my sending unit be bad? Could I have a leak somewhere? I can't seem to get an accurate reading - though it does progressively move towards E - it still pops back up upon acceleration. Thank you for any help.

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yeah. Its an easter egg of GM's engineering department. Not only is it a fuel gauge, its an accellerometer too! :lol:

 

Mine does that. And whoever says it sucks is lying, they just wish their dashboard was as animated as ours are.

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When accelerating it goes up, when idling it moves back down.

 

This is an analogy to what your peen should be doing as you hit the gas!

 

Truer words have never been typed! LOL!

 

What do the other auto manufacturers do differently that allows their fuel level sensors to be more accurate?

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I know on Suzukis the guage is controlled by the BCM. In "normal" mode the guage will go from F to E in 55minutes - so the level bouncing around has no effect on the guage. There is a small flaw though if people refuel with the key on the guage will still be in "normal" mode and the guage will go from E to F in 55mins lol..we've had people come in saying they filled up and the guage is stuck at E but it will go eventually to F.

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I know on Suzukis the guage is controlled by the BCM. In "normal" mode the guage will go from F to E in 55minutes - so the level bouncing around has no effect on the guage. There is a small flaw though if people refuel with the key on the guage will still be in "normal" mode and the guage will go from E to F in 55mins lol..we've had people come in saying they filled up and the guage is stuck at E but it will go eventually to F.

 

sounds like my mom's F150... she filled it up once with it running and it still was on E when she was done... freaked her out for a few minutes.

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There is one thing that is possible to cause a float problem.

If the fuel tank has been changed the new tank may have no baffles, or if it does they are probably not in the same place as the original ones.

My cutlass never did that until i repllaced my fuel tank

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I have never seen an 80's / early 90's GM fuel gauge that did not move all the time.

 

Fixed.

Truth. According to the gauge, I'd sometimes lose or gain a quarter of a tank in the Beretta, depending on how fast/sharp I took the curve.

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Here's a question I'm not sure if I've ever seen an answer for.

 

On the cars with the DIC... the DIC appears to be vastly more accurate than the regular gauge.

Granted the DIC is calculating estimated miles remaining, and the dash gauge is calculating volume of fuel remaining... but I would assume both get their data from the fuel level sensor?

So why does the DIC estimation not fluxuate as much? Or is the stability of that estimate an illusion that GM pulled out of their hat somehow?

 

(well, my DIC miles remaining fluxuates plenty... but only down... sometimes 5-10 miles remaining at a single jump... but my rotted out gas tank prolly has more to do with that one.)

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the DIC records fuel level over a period of 2 minutes and then spits out a number as an attempt to give an accurate number. that's why it doesn't flucuate as much. the sender is more or less directly connected to the guage on the dash, there is no buffer to try and smooth out the operation.

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the DIC records fuel level over a period of 2 minutes and then spits out a number as an attempt to give an accurate number. that's why it doesn't flucuate as much. the sender is more or less directly connected to the guage on the dash, there is no buffer to try and smooth out the operation.

 

Crap... you just beat me to it!

 

Side note here, I'd expect the DIC calculates milage also based on injector pulse, no?

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Crap... you just beat me to it!

 

Side note here, I'd expect the DIC calculates milage also based on injector pulse, no?

 

the ECM spits out some info to the DIC, such as MPH, "accumulated fuel" and injector flow rate. i'm assuming the accumulated fuel accounts for a couple of the operations necessary to determine an accurate MPG number.

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the DIC records fuel level over a period of 2 minutes and then spits out a number as an attempt to give an accurate number. that's why it doesn't flucuate as much. the sender is more or less directly connected to the guage on the dash, there is no buffer to try and smooth out the operation.

 

Crap... you just beat me to it!

 

Side note here, I'd expect the DIC calculates milage also based on injector pulse, no?

 

So is it using that once-every-two-minutes data from the level sensor to auto-correct it's estimate based on the last known reading combined with the instant injector pulse data? That would explain why a fuel vapor leak from the tank area would cause the DIC reading to jump downward in large increments every so often instead of just an overall more rapid decrease.

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