I have tried reading the posts here and the diagnosis part in the chassis service manual but no luck. I had the dash apart a few months ago to replace the shift indicator and after it was reassembled the fuel gage went to past full with the key on. I have the dash out again thinking that it was a loose connection but can not get it to work right. The manual says to hook up the test unit that simulates the tank sending unit. I have a multimeter but am only know how to check the voltage and if the circuit is open. Update: The gage will go to E when grounded at the tank sender connection. Therefore either the sender is bad or the wire from the sender to the connection behind the bumper is bad. I guess that I will try to run the car out of gas and see if the gage drops to E if not drop the tank. Thanks Keith
The service manual would probabnly have suggested wiring a 90 ohm resistor in line to see if the gauge works (fyi: the fuel sending unit measures resistence) However without a 90 ohm resistor the manual is a paper weight. The best advice I could suggest would be to test the ground circuit to the gauge and see it's grounding somewhere along the line. I had the exact same problem after I lubed up my speedo-cable years ago and it turn out I had accidently chaffed the ground wire of the gas gauge, so it keep register full (or maybe empty... I'm to tired to think straight :sleep: ) The other rather ugly alternative is to undo the your work on the shift indicator and see if that makes a difference. But as I said, I highly suspect that you have a lose ground or shorting ground, so that the gauge is reading no resistance (aka. FULL). I hope this helps, let me know.
I fixed this same issue last week, after I bought a good fuel sender from a member.... But the fuel sender was not the problem. After the tank was dropped and replacement sender installed the fuel guage still read past full... I fixed this by breaking out the multi meter and the wiring diagram.. I traced the problem to a bad connection between the flat body cable and where it connects under the dash... I cleaned the connections with alcohol and bent the metal prongs inside the connector so that it would grab the metal pin better... That fixed my problem!! One trick to test for voltage or a short in a cable with out actually cutting the cable is to insert a small metal safety pin into the wire and then test the pin.. The pin hole that is made is so small you don't have to worry about a short from leaving exposed wiring... Find out which color wire is responsible for the fuel sender then find that wire under the dash. Then start to test for voltage & shorts on that particular wire at every connection point from under the dash, to the connection to the flat body cable, to the rear of the car where the flat body connection connect to a wire that connects to the fuel sender... -Brook
This is what I have done so far. I took the dash out again and replaced the fuel gage. Same past full reading. The connection to the cluster got cleaned and touched up with contact grease. I still have the past full reading. I broke into the connection going into the flat cable. I have voltage going thru the tan wire from the cluster. I 'm guessing that that means that the connection at the dash is good? The dash lights work so that means the connection is grounded properly through the headlight switch. I guess the next point it to try and find a disconnect at the tank and see if I am getting voltage to that point from the dash? If the wire was shorted the manual indicates the gage would read past emtpy with the key on. So at this point it is a disconnect in the tan wire from the flat wire connector to the tank possible sending unit. Thanks Keith
