I'm having a (what I think) is a strange issue going on with a 93 civic coupe I bought recently. When I purchased the car it had a d16z6 block with a y8 head on it and would crank but not start. I ended up finding that the fuel pump was not turning on with key on (II) or cranking. I had already planned on replacing the engine anyway with a running z6 from a different 93 coupe I was parting after it was crashed. I had just yesterday finished the swap and I'm still having the issue with the running engine. After turning the ignition I can hear the main relay click on and off quickly and the fuel pump turn on but only for 1/4 of a second at most. My first thought was that the fuel pump was bad but while I was testing the main relay I had paperclipped pin 5 and 7 and also 1 and 7 and the pump turns on and runs just fine. I replaced the main relay and ECU from the car I'm parting and still have the same symptom. If it helps I tested power at the main relay connector with the relay connected and not connected. With the relay disconnected and key on (II) I have power and pin 1 and 5, and with the relay connected and key on (II) I have power at pin 1, 3, 5, and 8. I have a feeling a wire may be damaged/cut between but Im not sure what wires to look at between the main relay and ECU. Any advice would be great.

 

Since you already replaced the ECU and main fuel relay, it’s likely the old fuel pump. Remove the rear seat bottom section and see if there is power and signal at the pump wires.

 

Ok I have some updates, I took a test light to the fuel pump connector at the pump and the light does turn on but only for maybe a 1/4 of a second? I ended up backprobing the main relay wiring to force the pump to run and it pushed fuel out of the fuel filter just fine. I decided to try to start the car with the fuel pump hotwired and the car would only start with starting fluid. I haven't had a chance to see if the injectors have power yet but I have a feeling the injectors not firing and the pump not wanting to prime are related.

 

Make sure you have all 3 engine grounds secure and tight since you did the swap. Usually when you have to introduce starting fluid to start the car, it’s a grounding issue.

 

I'm really confused now, I did some cleaning/tightening with the grounds. I cleaned the thermostat ground, both grounding blocks in the engine bay, the valve cover ground, and the trans ground but no changes. I ended up unplugging stuff on my intake to see if there were any changes and for some reason when I unplugged the evap purge solenoid the fuel pump turns on for the right amount of time??
I also checked voltage on my injector connectors and found with the injector unplugged I have ~12 volts from the left side and ~3.5 volts from the right side. BUT when I unplug the evap purge solenoid the right side drops to ~0.5 volts. I think my next step is checking out the grounds inside the cabin but past that I'm kind of at a loss for why it's acting so strange.

 

The other thing I noticed was strange was that when I turn the key to ON (II) the check engine light does turn on, but theres a second or so of delay before it turns on compared to the rest of the lights on the dash. I only noticed that when I was borrowing a civic to drive to work and saw the difference in the timing of the light. Also the check engine light seems dim? I'm also not sure if thats simply the bulb or another sign of a damaged wire/ground.