engine wont stay running,dies after a few seconds past cranking on 1993 GMC Vandura 2500

when I cycle the key a few times, seems to build up fuel pressure fine. when I start the engine it runs a few seconds then dies out. I can see the fuel spray lessen at the TBI injectors to the point of just a few drops. I can do this over and over, same result. Seems that fuelpump must be working. I dont have FP gauge, Relay doesnt feel to click "off" by itself, put in a new fuelfilter.Can ECM cause this? This is van conversion, can't find the ECM, ideas?

Asked by for the 1993 GMC Vandura 2500
may not have enough pressure. get it checked by a shop to confirm.