1998 Chev Blazer, 4 doors, 4x4
The gas gauge is very erratic, it goes from empty to full and back whenever it feels like it. Sometimes it reads somewhere in-between but only for a moment. I always reset the trip odometer when I fill up; I always fill up between 150 and 180 miles. Could this be from a corroded ground strap, or is the sending unit the more likely suspect?

For 4 years it's been just an occasional driver when we get lots of snow or for Home Depot runs. Now It's my daily driver again since I got a job as a rural mail carrier. My route consists of only cluster boxes so it doesn't matter that it isn't RHD. If I stick with it then that might be a project

 

There is no way to know without proper testing. You would have to get under the truck and test the quality of the power and ground at the gas tank connections. Since the problem is intermittent it will be difficult to get 100% confirmation at the wiring harness but its a start.

George

 

Most likely case is the fuel level mechanism on the fuel pump itself. It has a couple of metal tabs that wipe across a PCB as the float moves up and down. Over the years the metal tabs ware away and start making less contact with the traces on the board. As you drive and the gas sloshes around in the tank, it wiggles the float around and will make the contacts touch on and off, so the gauge will just randomly work and then not work.

Went through the same thing on my 04. Dropped the tank, replaced just the float and electrical parts of it, then 2 weeks later the pump went out, so I had to drop the tank again and then replace the entire assembly lol.

 

I had same problem, which went away after installing new Delphi fuel pump.