I have a 2004 Tahoe 5.3L Z Flex that my wife drives. 1 month ago she drove out of a Burger King drive thru and it died. She could not crank it and ran the battery down trying. Had AAA tow it home. I thought it might be alternator but after replacing battery I load tested it and all passed and charging system OK at 14 volts.
Then this week she went to vet. Upon leaving the vet the truck cranked and she pulled out of space and it died. She called me and when I arrived (15minutes) she got it to crank and backed up into space. I rechecked alternator and battery ok, so I followed her home.
I replaced the fuel filter and then check fuel pressure per below:
Key on, engine off = 50 psi
Engine Running = 43 psi
Running and Unplug FPR vent = 50 psi
Engine Turn Off = 43 psi but over 10 minutes slowly drops down to 20 psi.
There are no misfires or codes on engine. The FPR and Injectors were replaced 1 year ago. Does this sound like a fuel pump?