The entire period of ownership of my 98, I have not had a working fuel gauge. It is not the sending unit, as there is a resistance reading of 80 ohms with a third of a tank reading off of the pump sending wires. It is not the instrument cluster as it came off a blazer I formerly owned, and it worked. I could use some assistance.

 

Have you checked for a broken wire from the sending unit to the IP. Not much else it could be.

 

Where have you measured the 80 ohms?

George

 

between the wires coming out at the pump.

 

i read somewhere that the is a direct wire from the computer to the pump for the sending unit, but for the life of me i cannot find a worthwhile wiring diagram

 

The black fuel sender wire at the pump goes all the way back to the dash and its grounding point is splice pack 422/423 on the left side of the dash. The purple wire goes to the vehicle control module, not directly to the fuel gauge. The VCM communicates with the instrument cluster with a multiplexed serial data line so it's not possible to isolate the fuel level signal, at least not for us lay people. What you can do is at least see if you still have 80 ohms between the dash splice pack (black) and the purple signal wire into the VCM on pin 13.

George

 

Are the dash "fuel level" gauge and "low fuel" indicator supplied with a same feedback line? If so, and if the "low fuel" is getting triggered, that would point some problems in between VCM and Your gauge, not the tank sensor.

 

Both fuel level functions are sent to the instrument cluster on the serial data line from the vehicle computer which gets all of its information from the purple and black fuel tank level sensing wires.

George

 

Did the fuel gauge work before the known good instr cluster was installed?

George

 

If your gauge reads full all the time you have a break (open) in either the black sensor ground wire or the purple signal wire. If it reads empty you have a short to ground.
You need to follow the wires from the sender to the PCM looking for damage, particularly around connectors. Quite often when engine or transmission repairs are done those wires get pulled out of their connectors along the way.