Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
There has been a service bulletin for that type of concern. Here is what it states.
File In Section: 06 - Engine/Propulsion System
Bulletin No.: 01-06-04-037B
Date: October, 2001
This bulletin is being revised to update part usage for C/K 3500 Models in the Parts information. Please discard Corporate Bulletin Number 01-06-04-037A (Section 06 - Engine/Propulsion System).
Some customers may comment on inoperative secondary fuel tank transfer pumps. In some instances, customers may experience multiple failures of the service replacement pumps.
This condition may be caused by the "Four Minute Final Pump Out" feature of the fuel level control module. This feature can command the transfer pump to on when there is no fuel in the secondary tank.
This command occurs with every ignition cycle for a period of four minutes. These transfer pumps can overheat and become inoperative when they are run dry.
Customers that never add fuel to the secondary tank can further compound this issue. In these cases, the secondary pump would become inoperative in a very short period of time.
Three new transfer pump modules have been released to correct this condition. The new module curtails the "Four Minute Final Pump Out" feature. When the sender in the secondary tank drops to a resistance reading of 2 ohms, the pump-out feature is disabled. At resistance readings greater than 2 ohms, the pump-out feature will continue to function. However, under this condition there should be enough fuel in the tank to prevent pump failure. Replace the fuel transfer module using the procedures and part numbers listed below.
C-Series Conventional Cab
Remove the component box lid.
Tighten the bolts to 30 N.m (22 lb ft).
T-Series Tilt Cab