Suburban will start run for 15 seconds and die

I am new to this forum; I am hoping someone can help me.
 
I have a 1995 Chevy Suburban K1500. It stalled out on me over a month ago the first signs pointed to the fuel pump. It would run for a couple seconds and then die sputter and die like it is out of gas, currently there is 3/4 of a tank. I replaced the fuel pump and fuel filter, but continued to have the same problem. It was then suggested that it could be the Oil Sending Unit, I had the oil sending unit tested and it is fine, still it will start run for about 15 seconds with the RPMs varying up and down and then die. After talking to a couple other people I was told to replace the PCM for the computer, again you can guess it didn't work. When I have tried a code reader that requires the car to be running I have gotten an error for the fuel pump relay so I replaced that. I have tried OBD1 and OBD2 code readers and I only get errors for the map sensing unit and fuel pump relay, both of those have been replaced and I am still having the same problem.
 
Does any one have any idea on what could be causing the problem? Like I said above it will turn over and run, well sputter, for about 15 seconds and then die. 
 
Could it be timing related? It seems like something is telling it to shut off.
 
Please help if you can I have already put a large amount of money on this and I don't want to spend anymore then I have to.
 
Thank you.

 

Before you move on to other things, check the fuel pressure while the engine is running to make sure it's up to specs.

Have you looked at the fuel filter?...maybe it is clogged solid

thanks for the replys i have checked both pressure and i have a new pump and filter

Give us a bit more back ground to help us trouble shoot the issue. Are you doing all of this work yourself........or has it been in a shop also?
 
Are you sure the cat isn't plugged? Does this thing have crank position sensors? I'm not sure. I can't remember, is this true fuel injection or throttle body. If throttle body have someone give it a shot of fuel right before it dies to see if it keeps running. Also, have someone have a multimeter on the fuel delivery 12 volt wire to make sure it stays at 12 volts and isn't dropping off to say 3 or 5 volts. Recheck all grounds also.