1999 Chevy Tahoe

you may have flooded it if it ran before. which in this case you put the accelerator pedal to the floor and see if it will start. If not then check for spark. you can go to tune up on this site and it will tell you how to check everything ifyou are mechanically inclined and have a volt ohm meter. Also if your service engine light is on then you'll need to get it scanned to see what has failed. If it's not, check the crank and cam sensors as they can be bad and not set the service engine light.