Turn key wont start- it cranks

Do you have a check engine light, what is the code. Do You have fuel pressure. You changed the fuel pump but is your fuse and relay good to the fuel pump. When you turn the key on do you hear the fuel pump kick on. It should come on as soon as you turn the key on, not just when you try to crank it. If you have a code it would help.

fuel pump should only run for about 15 seconds when u first turn the key on now you should check to see if the fuel filter is clogged or your sending unit might be bad on the fuel pump itself

Probably the crank sensor, do you hear the fuel pump 'buzz' when you turn on the key (not cranking the engine, just key on)? If you do hear the fuel pump (only lasts about 2 seconds), it may be the ignition module, otherwise it is probably the crank sensor.

check for fuel pump relay not working

verify that you have a fully charge battery and that you have the same amount of voltage at the battery as at the starter when the key is turned to the start position. If not repair fault at positive cable either at battery or at starter. If voltage checks good. Use a remote starter and turn key to the on position and try to crank over engine with remote starter. if engine cranks over. You have a defective starter solenoid and starter must be replaced.

listen for a buzzing sound in the rear when turning the key.
if you cannot than take off the fuel filter and let it hang down. than try turning on the key. fuel should spill out smartly. if not replace the pump.

yes you should be able to hear the fuel pump run for about 5 seconds once the key is turned to the on pos. check to make sure you have spark. if you do try having someone spray air intake or carb cleaner into intake manifold while you crank. If the truck starts right up for a second (or stays running as you keep spraying) Id say you have a bad fuel pump and id change the sending unit also. (First check the fuel pump fuse and fuel pump relay) GMC and Chevy are nororiously known for having bad fuel pump/sending unit problems. I have prob changed over 60 myself.

the filter on fuel pump might be clogged as well or fuel pump needs replaced

I CHANGE CAM AND CRANK SENSOR,FUEL PUMP,COMPUTER BRAIN BOX AND COIL PACK STILL GETTING NO FIRE UNLESS I JUMP A FIRE WIRE FROM BATTERY

check fuel pressure.if not above recomended spec. replace fuel pump. for starting have solenoid 0n starter checked.