1990 Honda Civic Intermittent Start Problem

My wife’s car has a starting problem that I can’t seem to solve. We are the original owners of her 1990 Honda Civic LX Sedan with 276879 miles. The vehicle is in great condition with the exception of this year long problem that has become progressively worse during the last month. Hot or cold the vehicle will intermittently start. The engine rotates but will not start. After 5 minutes it starts right up. I’ve done a self diagnosis observing the ECU and the LED flashes 16 times indicating faulty fuel injectors. So far, I’ve replace the fuel injectors with 2 used ones with 153k miles and the fuel pressure regulator without resolve. The fuel pump and alternator have been checked and are operating properly. Last month I replaced the distributor with a used one with 128k miles due to an unrelated problem and put on new spark plugs and wires. Do you think changing the main relay and/or putting in new fuel injectors would solve this problem.

Please help before my wife kills me. PS-I am by no means a mechanic. The Haynes Repair Manual has been guiding me thus far.