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Discussion Starter · #1 ·
How exactly is the instrument cluster getting the fuel level information? I had a low tank yesterday, how low I'm not sure, SID's DTE and the fuel level guage were moving all around each time I restarted my car; at one point I had the reserve light on with 60 miles left, later made a stop back at the office, started again and was apparently then out of the reserve area and back up to 90 miles, parked the car on a very angled edge of roadway, driver's side on the bottom of the slope, and when restarted the SID then read 4 miles left and the fuel guage at the bottom, reserve light on. Drove to gas station with those two sensors reading that I had nothing left, put two gallons in and SID jumped back up to 130 miles. So either the sender only reports once at startup and the fuel level then derived from monitoring the fuel consumption rate one of the injectors, or I've got a sticker sender unit. Can one gain access to the sender unit in the tank somehow?
 

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My 9-5 does exactly the same thing...reserve light comes on DTE shows 60 miles left. Park facing downwards on a steep hill, start up and i've now got 1/4 of a tank and 140 miles DTE. Its got to be related to where the sender is in the tank, park on level ground and nothing changes. :roll:
 

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Yep, the float is situated at the back of the tank. Vauxhall Cavaliers were notorious for over and under estimating how much fuel you had, due to the shape and position of it. I speak from bitter having-to-walk-to-a-petrol-station experience

If I'm feeling pessimistic about the level of fuel in the Swiftmobile, I tend to park it uphill on our slope to the garage :D
 

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Discussion Starter · #4 ·
Damn, broke out the Haynes manual. Haynes has a great way with words :roll: :
"Fuel guage sender unit -
On all models, the fuel guage sender unit is integral with the fuel pump; refer to section 9 for details."

Guess I won't be fiddling with that for now.
 

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Related to this...I know that the mpg estimate on the sid is based on the last 20 miles or last reset. However I have the impression that the DTE is more or less instantaneous, if i'm coasiting downhill it seems to be much more optimistic than when I climb the next hill. Does anyone else think this is true, or am I imaginining things? It isn't as dramatic as hitting the reset while coasting down a long hill, but it does seem to change quite a bit depending on how I'm driving.
 

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JMarkert said:
I have the impression that the DTE is more or less instantaneous...
I believe that is correct. It seems to recalculate the DTE with each update of the display. Reason for this is that if the DTE were calculated using the same averaging method as mpg, you could run out of gas with no warning... say you get off the highway with a small amount of gas left, if the DTE is based on running 30-34 mpg and you drop down to 15-18 in traffic... you would run the tank dry with 25-30 miles DTE left on the display (!)

JMarkert said:
I know that the mpg estimate on the sid is based on the last 20 miles or last reset.
It may just be the last reset, definitely more than 20 miles, at least on my car, with the SID-3.
 

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It may just be the last reset, definitely more than 20 miles, at least on my car, with the SID-3.
I think I agree with this too. My owner's manual says 20 miles or last reste, but yeah, it definitely seems longer. I took a long trip a couple weeks ago and have done just city driving since but the mpg's are still near the hwy range.
 

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JMarkert said:
I think I agree with this too. My owner's manual says 20 miles or last reste, but yeah, it definitely seems longer. I took a long trip a couple weeks ago and have done just city driving since but the mpg's are still near the hwy range.
Yes, I would have been surprised if this had changed between '94 and '96, unless it is a SID-2/SID-3 difference... then again, if I lose any more pixels on mine, it will not matter much <chuckle>
 

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Discussion Starter · #9 ·
My impression of the whole system is that the DTE is an average of the last 20 miles while the mpg is the cumulative average since the last reset.

I'm curious, after filling up the gas tank and you reset the SID, what are you guys getting for a DTE number?
 
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