alright guys I got a 97 blazer 4dr 4wd and the fuel gauge has not worked since I got the truck back in June 2016. It says its full all the time and then out of no where it will start dancing around and going nuts and by going nuts I mean it does full 360 degree circles and hits my volt gauge. I would prefer to test the wiring before dropping the tank I just haven't been able to find a wiring diagram that matches the wires going to the computer so if anyone knows how to go about testing the gauge and wiring that would be awesome!

 

Very common for the sending unit in the tank to cause crazy readings. Very, very common.

 

Here is a mitchell wiring diagram. Apparently it covers S-10 and blazer since it shows both ECM's in the diagram. Just pay attention to the lower one (VCM) for your blazer.

 

Alright so I would want to hook an ohm meter to the PPL/WHT wire for the fuel level signal and try rocking the truck back and forth to see if it changes? Also to check the ground wire to make sure its good would I put a meter on the negative battery cable and then to the BLK wire?