67-72 Chevy Truck fuel gauge diagnostics 101

[TBONE1964]

Hello all,

It has come to my attention that there are a few people out there that are having trouble figuring out if it is there fuel sending unit, gas gauge, or something in between that is causing there fuel gauge to not read correctly.

My goal here is to show some basics and also show what happens when you loose ground or power to the sending unit or gauge. Please bare with me and ask questions. I am going to attempt to make this as clear as possible.

The first set of photos is showing what you have and what you need to diagnose a sending unit and gauge.

The two basic tools I use for my testing are a known good sending unit and a DVOM (digital volt ohm meter) set to the OHM 200 scale. For my testing I also use a battery carger set on 10 amp to simulate a 12V car battery.