Hi Rick...It can mean your sending unit is wearing out, and this is common. The original sender unit wore out in a way which over time causes it to do exactly what you've mentioned. The body was pot metal and there was only one pivot hole for the float shaft (you can see this in the images attached). As this hole wears larger and more oval shaped, that causes the wiper to contact the rheostat coil more and more intermittently. This tendency is worse when your tank is between 1/2 full and full (or when you are close to empty)...because that wiper is at the bottom of the rheostat coil when you're full (top when you're nearly empty) and it can move around more in that case. When that happens there will be areas on the sweep where contact is only made occasionally and eventually you will have areas at which no contact at all is made and your fuel gauge will fall to zero then. Personally I would remove the sender and check it. If the float arm wiggles easily around it is time to buy a new sender. Some say a picture is worth 1000 words. I'm sending you 5. Please look at the first one. That shows the orientation your sender rod is supposed to have. Image 2 shows what happens when it wears out...you can see the slant. Image 3 shows where the wiper is supposed to ride. Image 4 shows where it rides when things wear out. This sender came out of my 1952 pickup where it had fallen apart inside the tank. If you need a new sender I've had really good luck with those I've bought from an eBay seller (id is Renbusan):
https://tinyurl.com/y3lhydzg This 0-30 ohm sender is what you'll need and I prefer this one because the rheostat is a flat plane (not curved), the rheostat contacts are molded in place, plus the 0 ohm reading is 0 and the 30 ohm reading is 30. Be very careful buying a replacement unit if you need one. One popular seller of parts (whose name I won't mention) sold me one which actually was a 0-90 ohm unit on which somebody who made it had dribbled solder to reduce the overall resistance to "about" 30 ohms. That meant at points you had no idea how much fuel you had because those areas which had the solder applied registered the same ohms until the wiper got to the point where contact was made with a good part of the coil. You can see what I found when I took it apart to figure out why it wouldn't work in the final image. Good luck!
