1991 Chevy Suburban valve body injection:

Hook up a noid light to the fuel injectors and crank the engine it should pulse, both of them. If light doesnt flash then check for +12 volts at one terminal with key on and hte other one should have none, if there is constant ground or no ground when cranking you could have a cks problem or a error with your fuel injector relay if equipped. And maybe even a bad ECM.