Duramax Fuel Pump Relay/fuse Random Cut Out?

[badass56]

i work on a fleet of 03-07 chevy gm duramax trucks. once in awhile i get a call that they stalled out or just wont start, i try to pump the fuel pump on the filter and its like theres no psi... open the fuse box and pull the fuel pump fuse or relay out and switch it with the drl right beside it and it will start back up like nothing happened. afterwards you can switch the relay back to its original spot and it still fires up.

 

if any one has any info on why or what couses this please let me know!!