I have a 1997 GMC Safari-Van - AWD-V6 and my fuel gage is always reading Full and jumps around when the start the Van.
I have investigated the problem on line and some say it the sending unit in the fuel tank.
Has anyone else had this problem or have a suggestion on a way to check it out.

Thanks for your help.

Welcome to the forums.
Yes most of the time it is the fuel sender.
There is a float in there that goes up & down & wears out the electrical contacts, causing erratic fuel readings.
Considering the age, it would be best to just buy a complete new fuel pump assembly.
The quality/ correct part for your safari is CARTER P74752M, around $150 at RockAuto..

What Soft Ride said ^^^^^^^

. . . and I believe your car is the right generation that cuts power to most things while the starter is being engaged. So:

Click 1: Steering unlocked, shifter unlocked
Click 2: Ignition on, beeps, gauges indicate whatever they think they should, and in the case of the fuel gauge it indicates full
Click 3: Unnecessary electrical stuff depowered (including gauges), starter engaged
Return to Click 2: Unnecessary electrical stuff repowered (including gauges), starter disengaged

Thanks for the suggestion. I'll give it a try and get back to you.

Chevy had a recall on the fuel sensor units but you are probably past the 100,000 mile limit on it.