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Discussion Starter · #1 ·
Ok to start with this is on the following:

1990 Mustang GT
5.0 stock motor
AOD transmission
Equal Shorty Headers
Offroad h-pipe
Pro-dump mufflers
MSD Ignition/wires/coil

I have owned this car for 7 years nowI don't exactly remember when, but the fuel gauge quit working one day (a long time ago). I never bothered with it, cause it's not my daily driver. However I have been doing quite a bit of work and would like to get the fuel gauge working again as it reads empty all the time. The gauge used to read when I first got the car and maybe 2 years after I had it the gauge went out. First by only reading 1/4 (when full), then 1/8 (whn full), and then Empty all the time (even when full)

Today I decided to put a new fuel pump in the car cause the old one was making all kinds of noise (it had been in there since before I bought the car), so when I placed the order for the fuel pump, I went ahead and got a new sending unit.

While the tank was down, I hooked the new fuel sending unit to the wiring harness with the sending unit out of the tank so I could move the float and see if the needle moved. However when I did this the gauge stayed on EMPTY. I ended up installing the new sending unit in the tank anyways, and after decided to check for voltage at the wires going to the fuel sending unit with a test light checked for current, and the test light did not light.

Now I am stumped and curious.

Are the fuel sending Units wires suppossed to have current running thru them?

Are the wires just a ground that the sending unit regulates the ground...thus giving the the fuel gauge by changing the resistance in the ground?

I know there is an anti-slosh Module in the dash cluster somewhere (suppossedly if this goes out it would make all the gauges read inaccurate or jump is what I have read <all my gauges work except for fuel gauge>)

I know the gauge itself can go bad (but that is why I was wanting to know if the fuel sending unit is suppossed to have current going to the lines or if it the wires are grounds)

Well any help and information would be greatly appreciated as far as what I should do to diagnose this to get it fixed.
 

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Discussion Starter · #3 ·

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Got it working. it was a ground screw behind the dash that wasn't making good connection.

cq90stang,

My son just picked up a similiar car, 90 LX and the gas gauge is not working also. Before I start a lot of trouble shooting on this issue with the car, where was that grounding screw exactly located behind the dash? It might save me some time and hassle.

AKCM
 
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