Truck shut down while driving now wont start. i hear the fuel pump engaging and can see the fuel going into the caarb when turning it over.

if it was the fuel pump engine should start with starter spray at least for a second or two, so, it sounds like your fuel pump is bad.
turn ignition to run and try hearing the pump run.

IT IS LOOKS LIKE A FUEL PRESSURE LEAKING INSIDE THE ENGINE OR DEFECTIVE FUEL INJECTOR LEAKING . TRY DISCONNECTING THE FUEL PUMP RELAY. AND CRANK THE ENGINE IF ALWAYS CRANK WITH OUT OF FUEL (CRANK WITHOUT START) YOU HAVE FUEL LEAK INSIDE THE ENGINE
REMOVE THE INJECTORS RAIL UP EVERYTHING CONNECTED,PUT BACK THE FUEL PUMP RELAY TURN THE SWITCH ON AND FIND WICH ONE IS LEAKING. (GASOLINE IS FLAMMABLE TAKE CARE)

We have a 2000 GMC 6500 454 engine. Truck will shut off, we turn off the the ignition wait for about 4 or 5 minutes. Doing waiting time, if you turn the ignition part way on, you can't hear the fuel pump, and if you try to start, it will not start . But after the 4 or 5 minutes, when you turn the ignition part way on, you hear the fuel pump, then it will start. It will shut down with a heavy load or even with out any load. It seems to do it more often when it's really hot out. It will shut down as much as 10 times.

sounds like a bad fuel pump. open the gas cap and listen when you turn the key to the on position, not all the way to engage the starter, you should hear a buzzing for 5 or so secands that is the fuel pump in your gas tank. if you dont hear that buzzing the intank fuel pump is probley not working.

Check your battery voltage, sound to me like your battery cold cranking amps is low. Its enough the power the lights but not turn the engine over. Have the battery replace

Was it the fuel pump? If not I would consider the charging system ie) battery, alternator or both.

I had the same problem and to my understanding blazers are known for their fuel pumps going out. You might hear the fuel pump engage but that doesn't mean it is putting out enough fuel pressure to keep the engine running. Your best bet is to have it towed to a local shop and let them run a pressure test to check and see if your getting enough fuel pressure or if your a big do it yourself type you can rent a pressure tester from auto zone or your local auto parts store. If you don't want to do that you can get a fuel pump for around 3 to 4 hundred dollars and replace it and see if that cures the problem.

The fuel filter could be plugged.

sounds like either your fuel pump went out or you have no spark going to your spark plugs check and see if you have spark first if so then open your gas cap with your ear next to the filler tube have someone turn key to run possition you should hear a humming noise for a few seconds if not then your fuel pump went out

usually if you have power it may be a fuel problem, when you turn your key to the on position you should hear your fuel pump come on, if not it could be the fuel pump relay under the hood or a possible bad fuel pump or bad connection on the fuel pump. hope this helps.