Fuel pump relay location

Where is the fuel pump relay located in a 99 Jimmy?? Wouldn't start the other day. Hit the tank, runs perfect. Any thoughts??

I think its under a cover on passenger side firewall

I have a '98.........check under the hood above the driver side front tire wheelwell....mine has a fuse block that has a plastic cover (looks like a covered battery box). Underneath the lid you'll see the layout of the fuses and relays. I know mine's there.....I've had to remove it several times to keep the battery from running down overnight. Key would stick in ignition........which in turn would run fuel pump relay keeping fuel pressure up to fuel rail. Hope this helps.