L31MaxExpress
I'm Awesome
I put a Racetronix harness on both the Express and Tahoe for this very reason. Forget the OE wiring, grab a Racetronix harness and be done with all the foolishness trying to make the under spec OE wiring work 25+ years later. My OE pumps were barely getting 10 volts with a harness that was in perfect condition and good relays. Pump gets within 0.2 volts of the alternators output stud with the Racetronix setup.