I hope we are able to resolve this technical issue:
my 2000 chevrolet truck /with service body, 2 wd, 5.7 gas engine.
it has dual tank . the truck work and operate just fine. the issue is the fuel level and tank operation. it seem I only fill out the rear tank which is about 14 Gal. that is because the Gauge show empty
while the front tank is full and never empty out.

I am not sure where to start. I checked the fuses , and relay all seem to be fiine

Any help would be appreciuated.

 

I had some problems like that, but I found that the connections/plugs for the Pump Assy and others underneath and in the engine compartment were dirty/corroded. I'd certainly pull them apart, brush/spray (possibly lube/coat) and reconnect to make sue that you had good contact.

PS;
Don't leave anything to chance, you might have to drop the tanks down, check if there's a connector on top of one/both.