My Honda will turn over but will not start. I have replaced the battery, the fuel pump, strainer, and the fuel filter. I have checked to see if the fuel pump was getting power and it was not. I checked the main relay and it was woring correctly, but when I put the relay back in the car, it started then. What could it be? What else could I test?

. Clean the main ECM ground, located on the thermostat housing.

. Check for intermittent ECM failure. Does the CEL always come on for 2 seconds and then go out, when the ignition switch is turned to ON (Position II)? If the CEL stays on, the ECM is likely toast, which is common on older Hondas.