91 honda civic hatchback won't start , has no error codes displayed on ECU anymore, I replace both injectors. But while driving check engine light comes on and car dies and won't restart. I replaced the main fuel relay and it did no good. What could I have left to replace?

When you turn the ignition switch to ON (Position II), does the Check Engine Light (CEL) come on and then go off after 2 seconds? If not, the problem is with the ACG (ALT) (S) fuse, in the under dash fuse/relay box; ECM (perform the K-Test); main relay; or the ignition switch. Perform tests in that order.

In your case, test all under dash and under hood fuses with a test light or multimeter. Likewise, perform the K-Test on the ECM--many are now failing on older Hondas.