Fuel pump just changed the fuel pump, and now we can't get it to pump gas at all. The old one at least was working part time.

first take starting fluid and spray it into the throttle body while someone starts the engine if it keeps running while your spraying the fluid into the throttle body then you must check the relay change with a new one if same condition then the fuel pump is not working check the fuse if that's good and the wires going to the pump are good and the fuel pump is good then go to the idle air control or the throttle position sensor but I think your fuel pump is the issue here or fuel delivery is not happening

This could be a few things. One is bad quality gas but since it started up again that may not be the cause. The other may be the fuel filter, fuel pump, or fuel injectors. Any of them would cause the engine to sputter and shut off. Do you normally buy fuel from this station? Was it a little old "Mom & Pop" station? They sometimes have dirt in their fuel. If not does the station you by from have pure gas, no ethanol. It's getting hard to find fuel that isn't at least "E-10" or 10% ethanol (alcohol). GM vehicles made after '97-'98 will run just fine on E-10. One thing about ethanol is it is basically like a solvent. We use alcohol to clean product before going into a paint process. It breaks down the oils and dirt. This can happen in a gas tank with ethanol. Especially if you have never or almost never used E-10 or higher fuel. Are you sure you didn't happen to buy E-85 fuel? Also, do you normally keep your tank at least half full? Sometimes a gas tank, fuel lines, or fuel injectors will have a varnish like build up and the ethanol will break it down and it will clog up the fuel filter, fuel pump, or fuel injectors. Do you know when the last time your fuel filter was changed? Then again it may be the fuel pump may be weak and/or about to fail. It happens and it can be expensive because the pump is inside the gas tank. I found out not to let the fuel level get super low, too. I let that happen one time while on the road and I almost couldn't get it started. One thing you can do to help extend the life of the pump is when you want to start your Tahoe, first turn the key to the run position without starting the engine. You get a lot of warning sounds for a couple of seconds but if you listen really close you probably can just hear the fuel pump pressurize the lines. It only takes a second and once it is pressurized you can't hear the pump. This will help extend the life of the pump as it doesn't have to work as hard for that short period of time during start. Most people will turn the key from OFF to START in one quick turn. Try to get into this habit for a while. It doesn't cost you anything and if it works it will save you some hassle until something actually completely breaks down. My son has an old BMW and he was complaining about having to put 2 fuel pumps in it in 2 years. I told him to try letting the pump charge the system before starting and he hasn't changed the pump in almost 4 years. Now it's part of the cute quirk of having a 32 year old car.

Are you certain you have fuel coming through? Best to check gas flow to make sure there is gas coming through lines. Did you change fuel pump with OEM or aftermarket? Electronic? All connections good and do you hear the fuel pump work? In my automotive life I have gotten a bad fuel pump before.

Also, not positive but I believe there are at least 2 fuel filters. I know my old Honda Civic had 3, so make sure you have identified where all fuel filters are.

Need more specifics regarding what kind of noise it is making, if any.

It sounds like your car isn't getting the proper amount of gas. You say your mechanic changed the fuel pump and the regulator. Id have him run a diagnostic tool on it to see if it throws any other codes. Its getting fire. Try changing the FUEL FILTER. it maybe clogged. maybe the pressure regulator is not giving it enough pressure to push the gas into the engine or maybe the fuel pump is only working at times. Does it run good and then start to spit and spudder then die? if so its not getting gas some how. Idk if you can adjust the pressure regulator or not. i mostly work on old school cars.

I bet it's the gas. After some time the gas will no longer be volatile enough to start the car. Try draining all the fuel and putting in some fresh gas. Remember, when you try to start it again you'll need to get the new gas through the pump and lines before it will start. Also, check the condition of the injectors. Old gas can start to break down and build up a film that could be on your injectors (or clog your fuel filter- better check that too). Hope this helps.

There is no need to bleed the fuel system. Do you want to drain the old gas? You can just disconnect the fuel line at the engine or if front of the tank and jump the pump relay socket to power up the pump.

yes it does need changing at the appropriate mileage requirement.

find the buzzing noise...likely its the fuel pump relay.

it is located in the gas tank