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Hello I have a 1995 saab 900 and the gas guage is extremely unreliable. I will fill up and everything will seem alright and the gas guage will read full. the problem is the next time i start my car the guage will read a random level and I have no idea of the amount of fuel I have. I have a system of filling up to the brim every 290 miles but this is unreliable becuase I ran out of gas at 260 today so I would apreciate any ideas or help anyone can give me. If anyone can tell me how to remove the fuel censor that would help greatly becuase I cant seem to find it.
 

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you may have 1 of 3 possible problems

1-- Bad sending unit on the gas pump. A real PITA to fix :x :cry:
http://www.thesaabsite.com/Saab-Fuel-Gauge-Issues.htm
Would involve buying a complete fuel pump kit too.
http://catalog.autohausaz.com/autohausaz/detailw.jsp?&partner=autohausaz&gkw=Saab%209-3%20Fuel%20Pump%20Assembly&gad=CI-R_J0DEggVjr57bHTqwhjtn_T8AyDPjdgT&make=SA&model=9%7Bembeddash%7D3-SEDAN-005&year=2002&category=E3001&part=Fuel%20Pump%20Assembly&sid=hlhexhyzmue4w555e0md3ce4

2-- A pinched hose on the EVAP valve. If your tank was dropped to change the gas pump, for example, the hose may have been pinched. Here are the symptoms.
http://www.townsendimports.com/Saab_TSB_Folder/Saab_TSB_pdfs/98_09.PDF
That's relatively an easy repair.
3-- Or you may have a bad cluster instrument panel circuit board
http://www.thesaabsite.com/900new/NG900faqs.htm#Dash+Lights+Go+Out+Or+Instrument+Gauges+Act+Strange
Here's how to take it out for repair or replacement
http://photo.platonoff.com/Auto/20051105.Saab_NG900_Dashboard_and_Instrument_Cluster/
 

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As I read the symptoms, the transmitter or sensor rheostat is weak and worn..The transmitter is a section of the the pump and unbelievably expensive as far as I know.
I "fixed" one in one of my old Saabs years ago just by cleaning and re-tensioning the rheostat - for the short term, this works fine..
The rheostat can be electrically checked using an Ohm-meter..
But, one man here bought an entire gas tank, complete for $10 or $20!! I guess that is what many do, if they can find a yard with 900ng parts...
 

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I've got a similar problem, the gauge reads full for the first 300 miles, then goes drops in a non-linear fashion.

When DTE is less than 90 miles, the needle is pinned below empty.

I would think this places the issue on the gauge circuit board. Is this something I can fix?

Thanks,

AD
95 900-SE
95k
 

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why rely on the SID's DTE? its not accurate, its value is calculated from data received from the ECM by the SID.

Use the old fashoned method, when you fill up, reset the trip odometer in the speedo and drive until you know the tank is emptyed, usually around 600-800 KM depending on engine and driving habits.
 

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Diosnoche said:
why rely on the SID's DTE? its not accurate, its value is calculated from data received from the ECM by the SID.
For me the DTE has always been consistent and linear, but the gauge is not. The guage goes from over full, after a couple hundred miles seems to drop a bit... then the last bit (under 125 on DTE) it fall under E.
 

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I believe the fuel consumption is calculated in part from the fuel injector cycle. If the fuel pressure is correct, and the injectors are clean and flowing well, fuel consumption and the DTE and MPG calculations should be spot on. If not, MPG on the SID will be different from MPG calculated from a fill-up.
 

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My current problem leads me to believe that the SID gets the fuel level from the instrument cluster. I say this because my instrument cluster is on its way out (fuel gauge drops, indicator lights come on, then 5 seconds later all is fine. Can be fixed by wacking the top of the dash above the speedo). When my fuel gauge drops because of this, the DTE on the SID also drops... not to zero, but far enough to be noticed (i.e. from 275 miles to 95 miles). The SID calculation will remain incorrect even after the fuel gauge returns to normal. The DTE slowly rises, but not all the way back to original. The SID often isn't completely corrected until I restart the car. I believe that the WIS talks about how the SID gets the fuel level from the instrument cluster when the car is first started.
 

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Slightly off topic, but I thought I'd ask anyway... Just recently I have noticed that during town driving my litres per 100km reading on the SID slowly increases from it's normal 10.9 or 11.0 to about 22.0 increasing by 0.1 every couple of seconds, especially noticable when sitting in traffic. It then settles around 15.0 for a while. If I go for a long run, it goes back down to 9.0 or 10.0 Is this my O2 sensor maybe? I also have an intermitant CEL...
 

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Frogdude said:
My current problem leads me to believe that the SID gets the fuel level from the instrument cluster. I say this because my instrument cluster is on its way out (fuel gauge drops, indicator lights come on, then 5 seconds later all is fine. Can be fixed by wacking the top of the dash above the speedo). When my fuel gauge drops because of this, the DTE on the SID also drops... not to zero, but far enough to be noticed (i.e. from 275 miles to 95 miles). The SID calculation will remain incorrect even after the fuel gauge returns to normal. The DTE slowly rises, but not all the way back to original. The SID often isn't completely corrected until I restart the car. I believe that the WIS talks about how the SID gets the fuel level from the instrument cluster when the car is first started.
If i have the system straight: since it effects the SID-DTE and the gauge, I'd suggest a bad lead from the sendor unit in the dash to both the SID and the gauge. Of course if banging is just a placebo effect.... then the sendor on the pump is much more likely
 
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