i have an 88 hatchback with a swapped b18 motor that just recently had trouble starting. sometimes it will start but will die after driving several miles. after waiting a couple hours it may start again but not consistently. it could be main relay, fuel filter, fuel pump, ecu, or just bad wiring. just not certain at this point...

 

When it doesn't start, check for spark.
Also when you turn the key to ignition ( before cranking) you should hear a faint whirring. This is your fuel pump priming. A relay should click and the cel should go out when the whirring stops. If not, it's probably your relay.