I have a 96 Honda Accord and like many others I am having the same issue. Turns over but won't start. When you turn on the key, the "D4" light would come on and you could here the fuel pump at that time. Now, none of the above is happening! I have checked grounds. New fuel relay. The ignition was changed out about a year and a half ago, (junk yard part), and it's got some play in it.

 

Are you able to make communication with the PCM; do you have a scanner that you can hook up the OBD connector and does it communicate with the PCM?

 

I'd bet that the ECU has failing electrolytic capacitors in it. Over time they dry out or leak and this causes odd operating issues and no start issues as well. If possible see if you can borrow a known working ECU and install it in place of yours ....does it work perfectly. The cheapest solution is to open up the old ECU and replace the failing caps which if you know how to soldier costs only a few bucks and some time.