Fuel Gauge reading wrong

M

Mrneg9

Get Some !
Joined
Feb 10, 2008
Seen a couple people on the forum with the same problem but nobody really giving an answer . Recently went to get gas filled up the tank. Gas gauge only read half tank. After driving car a couple miles gas gauge did go to full. Next time I went to start the car gas gauge only read half tank again. Drop the tank replaced the entire fuel sending unit along with fuel pump. Also installed hot wire kit. When done started car up gas gauge read empty. Went to gas station filled up gas guage once again reads half tank. While driving home gas gauge goes to full. Obviously the sending unit wasn't bad it must be something else any ideas? I did pull the dash cluster out and checked the terminals where the cluster plugs in at reassembled with a little electric grease. Still reads half tank.

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Where did the sending unit come from? The new one.

"Obviously" is a bad term to use with these cars. Especially if you have purchased a starter, alternator, maf, fuel pump, coil pack, tps, brake switch, tcc solenoid , etc from autozone, o'reilley, advance, pep boys...The list goes on.
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I am having a similar problem. Mine is reading low. Doesn't go all the way to full, about 7/8 , and when on E, still have about 4 gallons left. Put a brand new Racetronix sender/pump and same thing. I think I read somewhere that the connections or terminals in the dash need to be hit with a copper brush or something. Let me know if you fix it.
 
The car is stock I'm the second owner. Car has 57,000 original miles. I try to stay with all stock GM parts if possible.

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I down loaded a picture of the analog dash and it does show two pins on the back of the analog fuel guage that they say get corroded. It confused me as I did pull the dash cluster out and did not see the pins there. You would think they would be right behind the gauge itself. Nothing there but bulbs and ribbon wiring ?

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Well went out today and check all the connections at the tank. Pit some electrical grease on the plug from the sending unit and the gauge seems to be reading correct now.

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Are you talking about the connection towards the bumper or the connection at the sender itself?
 
Was talking about connection at rear bumper. But today same old crap. Turned car on fuel gauge went to 3/4 tank. Just the night before I went to gas station one block from my home. Filled the tank. Read FULL. Went home parked it. Today 3/4. Even got a gas can and filled tank to top. Still 3/4. Really starting to be a pain in the ass. Looks like Im going to have to drop the tank again.

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Same problem here, three sending units later and still can't figure it out. :(


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Same thing happening on mine bounces back and fourth. At start goes passed full then as im driving for about 5/10 min goes to were it needs to be well shorta. Like its playing with me... dam autometer gauge!!!!

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Fuel gauge was on 1/2. Filled up. Took 9 gallons. OK we're doing good. Turn car on needle goes to about 1/16 past F. The joys of driving a 26 year old car;)
 
Start with checking for hi ohm readings on the tank chassis, and hanger grounds, etc.
As for the Autometer ga..Same thing. AM tech says <.2ohms. More than that, is a problem w/ accuracy.
 
Everyone always assumes it is the sender. Here was my fix:

1) Full tank of fuel
2) Remove gauge and tighten down the three screwed on prongs
3) Use very small needle nose pliers to hold the small disk the needle pivots on stationary, while carefully rotating the needle to the "F" mark
4) Reinstall
 
so ive read all I can I this
mine only reads half full when actually full
gonna start with easiest which is plug at the back
next sending unit itself bc what ive read the OEM ones not great but why would that be the problem
shouldn't it just work or not work at all
then on to the instrument cluster
any new insight on this problem
 
The gas gauge sending unit is just a variable resistor. It's resistance is 90 ohms when the tank is full and zero ohms when empty. It is linear so 1/2 tank is 45 ohms, etc. You'll need a volt-ohm meter to troubleshoot it.

Two wires are used to make it work, a pink wire for the gauge and a black wire for ground. Any resistance in either circuit (corrosion) will make the gauge show higher than normal. But this is not your problem since it often shows 1/2 when it's actually full. I would measure the resistance starting at the back and working my way up to the gauge. The ground wire is attached to the body in the trunk, left side rear corner. The pink wire goes through a 3-pin connector behind the bumper, then it goes to a 6-pin connector in the trunk near the ground connection (photo attached). From here, the pink wire runs up to where the fuse panel is under the dash.
Trunk-C320-G177.JPG

Measure the resistance between the pink wire and ground at the bumper then again in the trunk. If you can jiggle the wires and keep the meter leads connected, you'll see the resistance change when find the poor connection or bad wire.
 
I bent my float arm inward a few degrees to get a more accurate reading on the gauge. I have a vdo gauge.
 
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