Hi everyone I am working on resolving this problem on my 1970 Buick Electra. I noticed that the fuel gauge reads full on the time. I disconnected the Tan (hot) wire to the tank and this did not change anything on the gauge. I tested the Tan wire and it did show 12 volts. I then checked the black wire which is ground from the tank to the frame and this need to be cleaned. I cleaned up the ground and still no change. I connected a wire to the black ground cable and ran it to my Ohm meter and then disconnected the tan wire from the pigtail at the bumper connection and this wire went to the ohm meter and nothing showed. If I am right about this the black ground connection that goes to the fuel sender in the tank and or the tan (hot) connection at the fuel sender on the tank could be the problem? Or is it possible that the sender is the problem. Connecting the ground wire and the tan wire to my ohm meter should have shown a valid connection. If the wires are firmly connected to the sending unit then is it the sending unit that needs to be replaced and I noticed that Summit Racing has a GM Sending unit (#VDO-226008 - VDO Fuel Tank Senders Unit, Fuel Level, 0-90 Ohms, GM, ), would this be a desirable replacement? Thanks
Im not sure about the VDO sender fitting your tank. Although its calibrated to work in a GM application, I suspect its a universal fit. Universal fit sometimes means it doesnt fit. Sounds like its just got grounded properly. Peel back some of the insulation of the ground wire. Make sure its not corroded under the insulation. make sure its got a good ground to the body First rule of electrical diagnostics- Check your powers and your grounds.
I have a feeling that the ground connection and the tan 12 volt connection to the sender unit at the tank could be the problem. I am going to have to drop the tank so that I can access these connections and insure that they are good. I noticed the VDO sender unit at Summit and was thinking a little ahead if the problem was the sending unit. I will check the connections right at the sending unit and go from here. Hope that the sending unit is not the problem, I know that these are next to impossible to replace. Thanks
The sending unit was a problem in the '70 LeSabre I had. I had to drop the tank, remove the sending unit and clean goop out of the contacts in the sending unit. If your car wasn't run much, that could well be the problem. Instead of reading full, mine read empty most of the time... ou:
Take your tan wire & ground it directly & give it a good ground. The gauge should go to empty. If it does the wiring from the sender & the gauge are good & there's something wrong with the sender. If it does not there is a problem with the wiring or the gauge itself. Many times the float goes bad & just replacing that will be all that's needed. While you have it apart clean the contacts inside the sender. These can be rebuilt.
I checked the connection with a ohm meter, I disconnected the tan wire (hot) from the trunk and connected it to my ohm meter. I then connected my ground wire (black) to the other end of the ohm meter and got no reading at all. It should have shown something. It appears that the connection at the sending unit is the problem, could be the ground (black) or the tan wire (hot). I will have to drop the tank and have a look. Also the car was sitting for 15 years and I know that the sending unit is probably gummed up to.
Your using an Ohm meter to check an Ohm meter, the tank sending unit. Do as I said & have been doing for 50+ years & ground the tan wire!!!!! It won't hurt anything & you will then be checking all the wiring to the front of the car including the gauge & all connections in between. Very simple once you understand.
I will go with your suggestion and update you on it. Electrical issues have been a bit of a problem for me to understand, but I am learning. That reminds me, I did check the Tan wire with my circuit tester to a good ground connection within the trunk. The circuit tester did light up, indicating 12v but the gas gauge still remained full. Thanks
Like I said, YOU NEED TO GROUND THE TAN WIRE!!!!!!!! Using a test light is NOT GROUNDING the tan wire.
I just went through this with my fuel gauge. Once in a while it would read full. It ended up being there was a short under the back seat where my harness connected. Like Tom said. If you ground that tan wire it should go to E. If it don't check the gauge. If it's fine you have a short from the gauge to the sending unit. Ray
Ah I get it now, I will get out to the garage after work and ground the Tan wire with a jumper wire and see what happens. Thanks for all the advice guys.
