91 XJ Chassis wiring cleanup

Just wondering what wires/sensors/switches etc are needed inside the jeep to make the engine run, simple as that. I stupidly gutted the entire interior, dash, wires, hvac, and all, and am now having issues with keeping the vehicle running. It ran perfectly before I ripped it all out, and now fires up but dies as soon as I shut off the starter relay. I though possibly vacuum issues, though I plugged the vacuum port on the intake manifold for the hvac which should be the only vacuum leak I introduced with this project. Is there anything the ecu uses inside the vehicle to keep it running longer than a fraction of a second? FYI I've ran the car without gauges or idiot lights for a while now (gauge and diagnostic connector unplugged) and never had an issue, but maybe it has something to do with my problem?? Help is appreciated!

EDIT: I've determined the car turns off as soon as I kill power to the starter relay, not a few seconds after. I've read somewhere that the fuel-pump kicks on with the starter, and maybe whatever continues power to the fuel pump after the starter relay opens is not functioning, anyone have any idea what I'm missing?

Power to the fp ballast relay? Should be on driver side fender. IIRC the relay is used when cranking and then switches over in run. Id also double check everything on your ignition switch.