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NG900 & OG9-3 Workshop NG900 (1994 to 1998) & OG9-3 (1999-2002) & '03 Convertible Technical Forum

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  #1  
Old 13th July 2012
kaw550 kaw550 is offline
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Default Fuel gauge not working...correctly

My fuel gauge only goes up to about 1/8 of a tank when I fill it. The low fuel level light comes on after a few miles of driving.


The SID was telling me the DTE but if I remember correctly the highest it got was 39 miles (probably based on the 1/8th of a tank).

I was told the fuel pump was replaced and later found the receipt in the car. It was done at a high school. So, I am not sure what end of the car start at. Is it a known issue? Is there a traditional float on an arm? Could it be bent?

I would like to fix it next week but I don't know if I need parts and if they would have to be ordered online.


Any idea how far I can go on a tank of gas? I would like to get it as low as possible but I have no idea what that is.
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  #2  
Old 14th July 2012
kaw550 kaw550 is offline
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I got my copy of the WIS last night. Thats one of the most difficult apps i have used.
i tought it would have done a better job on the wiring.
If i want to check the ohms.from the sending unit, where is the harness i tap into?
Behind the dash? Under the seat?
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  #3  
Old 14th July 2012
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The NG900s have an access cover under the rear seat. There are two connectors: one for the pump and one for the fuel level sensor. You can figure which is which by turning the key to On and watch the gauge as you disconnect each connector.

I'm not sure if the verts have the access cover. Worst case is dropping the tank... Ron
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  #4  
Old 14th July 2012
madi139 madi139 is offline
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Default Has same problem

Hi I had the same issue on mine a few years ago. The gage would read full after a fill up and in two minutes of driving it would drop to empty and give me the low fuel warning. I know on my car with a full tank and my highway miles I get 330 to 350 on a tank.
This went on for a few months and then one day on the highway all the Gage's and lights went crazy and then my car died. Pulled over and Tried to restart car, everything lit up but I did not hear the normal double click and hiss of the fuel pump. I thankfully have a guy who replaced the pump for 350.00. Since then not a problem gage works great and Sid read out.
Here is a link I found back then that did help.

http://www.saabcentral.com/forums/sh...highlight=gage
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  #5  
Old 14th July 2012
kaw550 kaw550 is offline
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I didnt think 9-3's had the hole but i will check. I am trying to avoid dropping the tank.
If i find the wires, open would be empty and if i close the loop it show as full, right?

If that workss i assume the issue would be in the tank.
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  #6  
Old 14th July 2012
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http://www.saabcentral.com/forums/sh...d.php?t=119759
Study this and more
Assume nothing
The $900 part from the manufacturer includes the gage sender - this is where I suspect the trouble is.
The national problem is one of workmanship - "high school" speaks volumes - then the same sloppy workmanship filters into the general society.
In other words, you will have to re-do this FP task.
FP = fuel pump
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Old 14th July 2012
BobSaabit BobSaabit is offline
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Quote:
Originally Posted by kaw550 View Post
I didnt think 9-3's had the hole but i will check. I am trying to avoid dropping the tank.
If i find the wires, open would be empty and if i close the loop it show as full, right?

If that workss i assume the issue would be in the tank.
I think they all have a wiring access hole... but neither has pump access unless you cut it.

To answer your earlier question: a 9-3 gets a min of 23mpg city when in reasonable tune (no known issues). Typical is more like 27 city, 32 highway. 23mpg*17gals = 391miles on a tank min. If you fill the tank and don't drive over 300 miles, you can't run out. Chances are you could go more like 450 miles... but play it safe.
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Old 14th July 2012
kaw550 kaw550 is offline
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You are right. It does have the wiring hole. I opened it up and found two connectors. One white one black.
I disconnected them one at a time but didn't see the needle move. Probably because it is pointing to empty. However it does drop when i turn the key to off.
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Old 14th July 2012
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You can try running Techron Fuel System Cleaner through your tank. If you're lucky the sensor just needs a little cleaning.
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Old 14th July 2012
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i am going to guess these wonderful high school "mechanics" didnt line the assembly up. there are 2 lines, one on the tank one on the sending unit, if these are not lined up could cause the sending unit to operate incorrectly. my second guess is these "mechanics" bent the float arm
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Old 15th July 2012
kaw550 kaw550 is offline
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I am pretty sure I need to drop the tank.

I would like to test the wiring first. Under the plug in the floor there is 2 connectors. Each has four wires. The wise says the waire harness for the sending unit is brown. So that narrows it down to one.

It also looks like tthe wires are YE/WH and GY/WH. I assume that is yellow/white and gray/white. If I jump the two wires shouldnt the needle on the dash jump?

What if I ground the wires one at a time?
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Old 15th July 2012
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before you do anything let me check the sending unit I have outside
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  #13  
Old 17th July 2012
kaw550 kaw550 is offline
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Bumping my own thread. I would like to test it before i drop the tank.
just waiting until i drive another 75 miles.

Any info would help.
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  #14  
Old 20th July 2012
laxdudeee laxdudeee is offline
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The fuel level is determined by a float attached to the fuel pump sending unit in the fuel tank. I just did the job and can attest to how difficult it is getting the unit out without bending the float arm.

Bend float arm --> incorrect fuel readings. Mine reads 3/4 when its full right now, I need to bend the arm a little. Kind of pissed about that.

Its your call, buy a new assembly for $500ish or bend the arm back and hope it works properly (or use your odometer).

Edit: there is a sticky on this forum detailing taking the FP out of the car. I'm surprised at how much misinformation there is in this thread...
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  #15  
Old 20th July 2012
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Fox Fader Fox Fader is offline
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Please do it right and drop the tank and fix it. I looked at my tank one day and it looks quite simple to drop in comparison to some of the others I've done.
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  #16  
Old 20th July 2012
laxdudeee laxdudeee is offline
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I took one look at the strap bolts and did a big NOPE!

Why is that the only right way to do it? You are cutting metal that will NEVER be seen, and if done properly there is absolutely zero negative effects. Hell, even if you botched it there are zero negative effects.
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  #17  
Old 20th July 2012
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The J-bolts on my tank straps were rusted. I soaked them in PB Blaster over night and they still were impossible to remove. Five minutes of careful cutting with a die grinder, I had the fuel pump out... Ron
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  #18  
Old 20th July 2012
kaw550 kaw550 is offline
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I think were at about 210 miles since I filled it up. The pan is to get through 90 miles by Monday night. Then I am going to drop the tank. I don't think I could bring myself to cut the floor.

I assume if I max out at 1/4 tank the arm is bent up. Is the arm normally straight? Will I be able to tell if it is bent by looking at it?
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  #19  
Old 20th July 2012
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You really need to compare the level sensor to a known good level sensor as there are no measurements for the level arm in the WIS... Ron
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  #20  
Old 20th July 2012
kaw550 kaw550 is offline
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Can I buy just the sensor? I tried a couple of web sites and it looks like I have to buy the entire unit.
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