Wiring for gas sending unit to back of gauge.gauge works slow are not at all,are half a tank

GAS SENDING UNIT IN GAS TANK NO FUSE.

Nine times out of ten, it is the sending unit in the tank that is the problem. To check, use a sort jumper wire to ground the gas gauge wire to the frame while watching the gauge needle on the dash, with the key in on position.

Find the gas tank electrical connector by the tank. Pull it apart, and on the harness side of the connector, locate the wire going to the sending unit. I don't know what color it is, but the fuel pump wire is a pink wire with black stripe and there is a black wire for the ground. The other wire should be for the dash gauge's sending unit. Have a helper turn the key to on and watch the gas gauge for any perceptible movement while you use the jumper wire, insert one end into the terminal for the gauge's sending unit wire (this is on the harness side of the connector, not the gas tank side), and touch the other end to the car frame-you are grounding it. If the dash gauge is good, the needle should move a lot, usually will move more than half way, one way or the other. So if it does, you know the dash gauge is good, and the problem is in the sending unit.

If it is the sending unit, it is quite a job to drop the tank, pull it out from under the car, then pull the fuel pump and sending unit out. You might be fighting a lot of rust on an '89-get some penetrating oil. And look for the removal procedure in a repair manual. It's not terribly difficult if you are handy with tools...and like to get dirty. Those hoses on the tank have been stuck on there a long time. Good luck.

Power should goto the gauge, second wire from the gauge goes to the sender unit on the tank. If there's any other terminals on the gauge or the tank they will be grounds

It sounds like the ground wire to the sending unit(located in tank) might be loose. The ground wire usually starts at the top of the tank at the sending unit and goes to a portion of the frame. Or the sending unit could be going bad.

You probably have a bad sending unit for the fuel level in the tank. this would cause the gauge to be erratic when the level is below 1/2 tank and the float is moving around much more than when full. The oil pressure gauge problem could be caused buy a loose wire connection or a faulty sending unit.

the guage itself usually lasts the life of car, so it must be the sending unit in tank or bad wiring to the tank. check all fuses also.

It sounds like a problem with the fuel gauge sender unit in the fuel tank which has worn out and gone open circuit and needs replacing. Access to the unit is usually through a removable plate in the floor in the rear of the vehicle. Disconnect the wiring connector and any hoses and then remove the securing screws. Replacement is done by reversing procedure.

Your sending unit is bad.

Here is the circuit:

(+)———»IS———»VR———»G———»SU———»(Gnd)

IS: Ignition Switch
VR: Gauge Voltage Regulator (mounted with the gauges)
G: Gauge
SU: Gas tank sending unit

The gauge deflects through heating a strip of metal that bends when hot. There is resistance wire wrapped around that strip to heat it up. One end of that wrap of wire is attached to the gauge "voltage regulator, the other end to the tank sending unit. The "voltage regulator" cycles between conducting power from the Ign. Sw. to the gauge, and disconnecting the gauge from that voltage. The sending unit in the tank varies resistance in response to the position of the float in the tank. Full: virtually no resistance. Empty: a lot of resistance. When the tank is full, during the period the "voltage regulator" is on, the strip of metal heats up a lot, because the sender has almost no resistance. When the tank is empty, during the period of time the "voltage regulator" provides voltage, the strip barely gets heated, deflecting the gauge hardly at all, because the resistance the sending unit creates limits the current through the gauge.

You have almost no continuity through the sending unit except near full, and at a few other position. Replace the sender, and you will have a functioning gauge.

You are probably looking at dropping the fuel tank down and removing the float and sending unit ( all in one unit). Once it's taken apart, you may see that you can fix it or you may have to replace it.

It is likely that its the sending unit in the tank. One way to determine if its the guage or the sending unit is to ground the wire from the guage and it should peg out. If it doesnt then its the guage if it does then its the sending unit.