What does the smog pump look like on a 2004 Chev Blazer?

SOURCE: Chevy Blazer 1992 Oil Pump Change

you have to drop the oil pan to get to it...once the oil pan is off there are 2 bolts that holdthe pump in place,,,you will also need a new screen for the new pump.

SOURCE: 1999 chev blazer won't start new fuel pump

So, do you hear the pump buzz on, when key is on? If that's good, then check your ignition circuit: check for spark at a plug. Use insulated pliers, hold end of plug wire 1/4 inch form engine bolt or ground source. When cranked, you should see a bright blue spark. Yes? Try another plug wire, too. No? Try another plug wire. If you have NO spark, could be your coil, coil pack, crank position sensor, ignition module. I would recommend using a diagnostic flow-chart to go through the ignition circuit. That way, you are not replacing unecessary parts_Expensive! Of course, if you have spark at plugs, your ignition circuit is good! Then you have to look further, like your injector circuit. Good luck.