Like many of you I was quickly frustrated by the gas gauge. Other vehicles also do not have linear response but the Caprice sticks on full then goes to the half then drops to zero like a rock. What this means is that the bottom half of the gauge is really one third of the tank. I have talked with other Chevy owners and we are not alone with this issue.
The short version of this post is that I claim I can recalibrate the fuel gauge without dropping the tank. I also claim I can fix the needle stuck on full issue.
First a short message. If you do not understand any repair or modification on this forum do not start it. You are responsible for your actions and the results.
Second if you have questions about how to calculate resistance values. Google ohm's law, parallel resistance, series resistance and resistance color codes. You can find on-line calculators as well. For questions on gas tanks, fuel senders, and fuel pumps there are other threads for these or start a new one please. You need soldering skills and the ability to understand circuit diagrams. The resistors needed for this mod can be found on: fleabay, maybe Radio Shack, industrial electronic supplies, hobbie shops, and old electronics.
What I hope to do with this post is show you some information so you can make an informed decision on whether or not you should replace or clean your tank sensor. I also have a method of cheating to change the way the gauge reads.
The best place to start is the hardest work. Drop the tank and replace the sender. Have a look at this link:
If you are having fuel pump problems you could clean the sender or replace it while you are doing the pump. This link covers cleaning and the practice of soldering all the in tank connections:
The only issue with soldering is trying to get warranty if the new pump or sender fails.
My suggestions to the tank work are these: Have a look at the socket on the car side. If you plug your new tank harness plug into a 20+ year old plug that is not weather tight anymore you will screw up your new tank harness with salt, dirt, and old grease. It may also leak in water. If the car end is not perfect replacing it may save you headaches later.
The grounding in the trunk topic is good for a separate rant. Stock from the factory this single ground wire carries 16.22 Amps when the tail, backup and brake lights are on. Then add the fuel pump amperage to the same 14 ga. ground wire! From an engineering standpoint the first thing to do at the tank is supply a separate 14 ga. ground to the fuel pump/sending unit plug. A separate 14 ga. ground to each of the Tail light lens is needed.