99 Blazer won't start

It was running fine when I went to the store and after I come back out nothing.
It acts like it's not getting any gas.

I check the manual and it says the fuel pump relay is also for the oil pressure.

I crank it for about 5 seconds and the oil guage doesn't move at all.. I change out the relay and now the oil pump needles moves a little when I crank it, but it still wil not start.

I also don't have that humming sound from underneath the drivers side anymore when I turn the key on.

Any clues?

TIA

Tony:banghead:

UPDATE
While waiting on the tow truck I decided to pound on the gas tank and it started right up after that.

That's the first thing my brother told me to do to verify a bad pump.