Propane to gas problem!!!

I have a 93 chev 1500 with a 305 in it. It has been on propane since 93 and we are switching it to gas. everything is done and hooked up now but it will not start. the injectors won't spay. there is gas coming to the carb and the fuel pump is running. we put the fuses in the fuse box. we tried pooring gas down the carb and the truck will run then. is there something we did wrong? am i gonna need a new carb? any help would be appreceated.
thanks
Chris

there is a small computer brain box,,that has been installed on the conversion,disconnect the aftermarket computer