have a 2001 sierra 1500 4wd with the 5.3 in it. it is hard starting. it cranks for 15-20 seconds then barely starts. once its running it runs fine. i hooked a fuel pressure guage to the schrader valve on the fuel rail and this is what i found..

turn key to on position-climbs to 55 psi holds for a second or so the slowly drops to 0

turn key to cranking position-slowly goes back up to 55 and finally fires when it gets to 55.

it seems it gets pressure then loses it and as you crank it over it slowly regains pressure and starts. is there some sort check valve im overlooking. thanks

 

Yes,but the check valve is internal to the pump...sounds like she's bad.

 

fuel pump is new. came with a new harness.