Funny thing here, I have a Honda Prelude S model with a frank engine built by me. F22 block and cooling jacket block guard with new forged pistons and rods bringing the comp ratio up to 13.3 with an H23 head with the stock Prelude S wiring harness and computer. The car has an H23 distributor and stock coil pack. I had to modify the stock F22 coil pack bracket to fit the H23 head and I welded a joint and the welds broke off while driving on a bumpy road yesterday and the coil lost ground while running. Luckily it broke off while pulling into a gas station and it was the first thing I noticed when I opened the hood. But now, I have no power going to the main relay which means no spark/no fuel and the CEL light stays on and when I try to jump the diagnostic connector, no ECU response. The CEL stays solid and doesn't flash like it should. I am beginning to suspect that when the coil pack fell off the block it must have bumped against some metal enough to cause a power surge and short out the ECU. Does this sound about right with my diagnosis? I have checked everything else concerning wiring and the main relay works when I jump the contactor terminals with a 12V source and the connecting terminals all allow power to flow through. But the ECU is not sending ground to the relay allowing the fuel pump to turn on and the coil pack/distributor to energize. All of my chassis grounds are good and so is the ground to the thermostat housing. There are no broken wires in between the distributor/coil pack to the ecu itself so my only assumption is a shorted ECU. Any other input would be GREATLY appreciated because I really don't want to spend another $100 on this car because I just put down $1000 to do a recent engine rebuild, stage 2 clutch flywheel changeout, driveshaft replacement, shocks and adjustible coilovers with new front and rear camber kits, plus another $1600 on wideband o2 equipment, a turbo/intercooler setup with a hondata s300 kit for my ecu, I just really don't want to spend another $100 on something if it isn't the problem you know? So please anyone any input would be appreciated!!! Thank you!!

 

Well it certainly sounds like you're on the right track. If you can't get any response from the ECU when you try to jump the 2P connector, I'm not sure what else it could be. If you can, try to borrow an OBDII scanner and see if it can even connect to the ECU. If not, I think you've found your problem. Worst case, buy a new ecu and try it out. If it doesn't work, sell it off again.

 

Nope, I just bought a new and tested ecu and that wasn't the problem. I have no idea what happened by my coil pack falling off its mounting place. I am still troubleshooting the problem and I need to figure this out pronto. Any more suggestions?

 

Recap:
No spark
No fuel
No signal from ECU STILL after replacement
No signs of life from Main Relay
BUT
All dashboard lights and gauges such as fuel sender and temp come on fine
Car cranks but NO response from ECU or Main Relay

 

I fixed it, thanks anyways. Lots of wiring harness shorts here.