I have a 1999 cavalier i don't know what the gas gauge sending unit looks like under the car,,i see the gas tank,and in front of it,,i see 3 sets of plugs,i removed them and looked at my gauge after each one ,and my gauge still reads full...i need to locat the ground wire,,to mount to the car. please help.. thANK YOU..
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In the fuel tank there is a fuel pump module. The sending unit for the gauge snaps on the side of it. GM dealer has it. If you have around 100,000 mi or over that I would just change the whole thing.If it hasn't been changed before or don't know. The gas tank has to be removed to do any of it. On the sending unit had 4 or 5 tiny contacts and they would brake off. the new sending units are made better.
you should be able to find the fuel tank harness under the car near the fuel tank. If you look just in front of the rear axle on the drivers side you will see two connectors Unplug the connector with the grey, purple, black, and black/white wires.
Ground the purple wire. Turn the key to the run position. The gauge should read full. If it does you have a bad sending unit (the part in the tank that tells the gauge what the fuel level is at).
If the gauge still reads empty you have a bad gauge.
This problem is caused by a defective fuel gage sending unit, the sending unit is located inside the fuel tank and is part of the fuel pump module but is sold separately in a kit from ACDelco, to replace the fuel gage sending unit requires the fuel tank be removed from the car. Below is a price and part number courtesy of rockauto.com
ACDELCO Part # SK1189 SENSOR KIT, FUEL LEVEL PRICE: $102.89
The number most common cause of this problem is that the gas gauge sending unit (consists of a float and a variable resistor) inside the gas tank is defective. To replace the sending unit in the gas tank, the tank must be removed from the car. The fuel gauge sending unit is sold as a complete module that also contains the electric fuel pump.
The most likely cause is that the fuel sender in the tank is faulty or that the wiring to the sender is bad.
Less common causes are a faulty fuel guage or circuit in the instrument panel.
Test the sender as it is the most likely cause and easiest to eliminate.
First inspect all connections that are readily visible to insure that they are secure & free from dirt or corrosion.
Disconnect the fuel tank sender wire at the tank. The guage should continue to show full (ignition on). Ground the wire from the sending unit at the fuel tank to any good grounding point on the car. The gauge should go to "Empty". If it does this is a strong indicator that the sending unit is at fault.
Well that tells me that someone installed the wrong fuel level sensor. Your going to have to drop the tank and pull the pump and float assymbly out. Then go to a parts store and get a sending unit that has the opposite resistance of that sending unit. Just wait until the tank is empty so its a lot lighter. You can call the parts store or go down and see if there is multiple sending units. The sending units work by resistance, when the tank is full the float moves up and turns a wheel in the sending unit, which either removes or increases the resistance causing the gauge to lower. The sending units either give full resistance at full or no resistance at full and then changes as the level goes down until it does the opposite at empty.