Im having the same issue with my blazer and i can tell that the pump is not comming on. When you first turn the key to on, you should be able to hear the fuel pump come on for a few seconds. Im not sure if the tahoes are different but on my blazer there is a relay in the front fuse box labled fuel pump. it is about in the middle and there is four of the kinda in a row and the top one is the fuel pump and the fuse that runs it is the ECM B which is beside the relay on the left. From what i understand this is a common problem with the chevys and most recommend against using a cheap airtex, carter, bosch and recommend the AC Delco but i dont know if that is just for my truck or for most of the chevys. My truck was running great then when the wife was on her way home from getting gas, it just shut off completly. Like you said above, it will crank untill the starter burns up but 0 chance it is going to run. I checked my relay and fuse they were both good. im going to check the voltage at the fuel pump connector and if it is good there, then it is a fuel pump issue. sorry i couldnt be more help. As far as removing the gas tank, again this is for the blazer, most say there is a little vent valve that tends to break if you put to much pressure on it by lowering it before it is disconnected. Most seem to have issues with getting the fill hose and vent hoses off. Look around on blazer forums to get what im saying from the horses mouth but im not sure it will be exactly the same for your tahoe. good luck and keep us posted on your progress.