I've been having this problem for over two weeks now. My Blazer will start for a second then shut off. No bogging and I can't keep it running by pumping the gas. I have replaced the MAP, fuel relay, oil pressure switch, TPS, and the computer chip. My next and last guess of what part to check and/or replace is the computer motherboard.

It was a progressive problem. It started out dying, but then starting and driving fine. All the way down to dying immediately after start-up. It has been a progressive thing. What does that sound like? Computer? Wiring? A different part?

I've talked to almost 10 other people at various part stores, dealerships and mechanics. I need ideas.

Did any of them tell you to do some proper testing?
Like check for lose of spark or lose of fuel pressure or injector pulse?
MT

No they did not. Could you explain those to me and how to do them?

Ok
If you have a bad heart or pace maker do not try this.
Just Go to parts store and get a spark tester.
If good Heart.
First pull coil wire out of dist cap and hold end of it a 1/4 away from a good ground spot on engine and have someone crank engine.
Spark should jump out of the end of it to ground and bee good hot and blue with a good sounding snap.
Or if it bites you real good and curls up your toes you have spark!!!

Does it do all of that?

Pardon me butting in. MT is right do some checks. Check for fuel pressure, with the engine cold turn the key on for a couple of seconds and let the fuel pump run, shut it off, and hit the shrader valve on the fuel line if it has one, and see if you get a spray or a dripple. Could need a fuel filter.
Good luck.

Fuel filter is good. Fuel coming out of the injectors is clean and smooth.

Okay on the gas, must have spark initially. When the engine stops, can you turn around and restart it with the motor dieing again? and do this over and over? There is a point there where the ecm switches from stored start values to sensor data to run. I'm chasing a problem like this in my celebrity and the ecm made the problem different but did not fix it. Does it ever store any error codes?

No it does not store any codes. Among other people I've been talking to, it's down to the ECM and the distributor pick-up coil. I have a used ECM coming and I'm testing the coil tomorrow.

Reaplced the ECM and chip and nothing. Tested pick-up coil and it didn't have the spec AC volt measurement so I replaced it. I have to refigure timing. I think I reinstalled the distributor incorrectly. I will hopefully fix that tomorrow.

I gave up. Sent it to the shop.