2003 yukon xl turns over fine wont start.

Does fuel pump run ? Remove fuel cap. Have someone crank it for you,you should hear fuel pump running. If not bang on bottom of tank while cranking. If it starts fuel pump will need replacing , if not check for power to pump, if it has power,replace pump. If no power, check relay for operation

If the engine does not crank, I doubt it has anything to do with the fuel system. You would need to find out if you have power at the starter posts when the key is in start position. Will it crank in neutral, and is the security light flashing ?

It is not necessarily the flow of gas that is important. You need at least 40 pounds of pressure for the injectors to operate correctly.

Have a friend lay/sit/crouch by the back of your truck(Where the tank is), and turn the key on. they should hear a "whirring" sound.
If they do, the pump is fine(Check fuel filter). If they hear nothing, replace your fuel pump!

the fuel pump is cooled by gas so if u run it low alot or {OUT} it can burn it up
keep that tank at 1/4 or u will pay!!!

COULD BE DIRTY FUEL INJECTORS LEAKING WHILE ENGINE OFF FLOODING OUT SPARK PLUGS.TRY THIS REPLACE AIR FILTER.CLEAN FUEL INJECTORS BY ADDING A BOTTLE OF SEAFOAM TO 3/4 TO FULL TANK OF GAS SEE WHAT HAPPENS.

When you say "turn over" do you mean "it wont start" ? These two things are very different. "Wont turn over" is like when the battery is dead, you turn the key and nothing happens. "Wont start" is like it's out of gas. (the engine cranks but wont start.) I'm not being sarcastic or insulting, I just want to make sure we are on the same page.

One is a battery/starter problem and the other is a fuel/ignition problem. If it is dead like a dead battery, (except you know it's not because the headlights are still working, then you didn't run out of gas, seven gallons would have made it start. If what I just described is the case you may have a bad ignition switch. Kind of unlikley on somthing that new, but not unheard of.

These fuel pumps do not like to be run dry. They are meant to be submerged in gasoline for cooling. If it cranks but wont start it is most likley the fuel pump. I know, it seems crazy to put an electric pump in the gas tank but that's where it is. A new pump is going to cost about $300, plus labor. The tank has to come out...lots of fun. The pump sits on the very bottom of the tank and some times you can get them to run one more time by having someone turn the engine over while you bang on the bottom of the tank. It doesn't always work but if it does it saves you having to tow it some where to get it fixed. If you do get it running do not pass go, do not shut it off until you are ready to put a new pump in it. you wont get another chance. Since the part is spendy you want to make sure it's bad before you go buy one. Or pay someone to do it for you. Up at the intake manifold there is a valve on the fuel line (looks a lot like a valve stem on a tire) It is there for testing fuel pressure. Even if you don't have a pressure gauge, you can depress the valve ( be prepared for a healthy shot of gas, there is supposed to be about 50 psi) do this with the key in the run position. If gas just dribbles out...it's the pump.

if the gas tank is on E, then add 5 gallons of gas, if possible.

seems like you have a bad connection inside the tank at the fuel pump and it requires the gas to be at a higher level because its using the gas as a conductor to make the connection, i recommend you replace the fuel pump.

you are either lacking SPARK or FUEL. You put 5 gal in the tank, but is the FUEL PUMP working ? The lights and radio operating only indicate ther is power in the battery.. Hope this helps.