Has it got a catalytic converter?
If it does remove the exhaust from it and try again.
I got a free 99 Suburban that the PO did everything to to try and get it to run longer than a couple of seconds.He spent the better part of a week working on it outdoors before he walked away from it.Not that he was the brightest bulb in the set.
Sat in my yard for a few years befor i got it for being abandoned.I pulled it in the shop ,returned everything back to stock.It would start and die almost immediately.Up on the hoist and split the exhaust by the converter,fired up and stayed running.
The converter was plugged soild.I removed it from the exhaust and it runs great.I got about 2-3 gal of black soot from the exhust once it fired without any restrictions.
90 Chev 3500 c/c 4x4,6.2na,400 auto,4:10 gears.DSG Timing gears,main girdle, isspro tach, pyro,boost,oil and trany temp.Dual Tstats, High volume peninsular pump,on shelf, Custom turbo and intercooler 85%complete. Change of plans for the dually, it's going to get a Cummins. Both trucks are Blue 90 4x4 crews