I got a real good deal on a 98 Blazer 4x4. It will start but dies instantly,but will run on ether. Has new fuel pump, ecm, all new sensers throughout engine. Any ideas what else it could be. I noticed yesterday that on the fuel meter where the fuel supply line go in that it was leaking fuel. I beleive that this would cause pressure loss causing it not to start. Could that be the problem?

 

My first thought would be fuel pump, but you said that it was already replaced. I would suggest testing the fuel pressure and seeing if the fuel is actually making it to the motor. It could be possible that there is a problem with the fuel line or a really horrible fuel filter.