Hey folks I've spent the last two hours searching old threads and no one has quite had this exact problem (that I could find lol)

I have a CRX that I changed to MPFI and OBD-1 Vtec at one fell swoop. The car has no spark, and I've checked all the wires from the ECU to the Dizzy... TDC, CYP, CKP are all ohming out in the correct ECU pins at the ECU Plug (yes I've even checked them at the OBD-0 side and the OBD-1 side) The large black/yellow wire running to the Dizzy has power when the key is on. The injectors are firing, I've tested them all with a set of diode lights. I have taken the dizzy and ECU out of the car and put them in a 95 civic and it fired right up, which tells me the dizzy and the ECU are both working properly. The only thing I could find that is DIFFERENT than the 95 is the fact that the ICM wire (Thick white wire on OBD-0 or Green with a white stripe I believe on OBD-1) has around 10 or 11 volts on the 95 civic when I check it with the key on, and on the CRX it doesn't get voltage... maybe 1 volt or less. I've checked it and it goes to the right pins at the ECU, so why does the voltage vary from the EG to the EF??

I guess my question is... what does the ICM wire do and what is the voltage supposed to be at the dizzy with the key on? I'm guessing it is supposed to be 12 volts maybe? This car is driving me nuts and it's the second one I've had this problem with. I have another CRX that I had to replace the harness in because a bad main relay melted some underdash wiring, and now it has the same condition... Fuel injector pulse and no spark... that car is OBD-0 though and on that car the coil gets warm when the key is turned on whether you crank the engine or not. I am usually spot on with wiring but these two cars have me stumped. I've done quite a few MPFI swaps and never had a problem like this.

Please ask me any other information you may need. These are both customer cars and I'd love to get them running lol (I work at a performance shop and my boss has looked over the cars and he's stumped too)

Thanks a million H-T.

 

update... I added another ground directly from the dizzy bolt to the battery, cleaned the thermo ground and the tranny ground, still nothing. WTF is wrong with this car?

 

It sounds like you may have kind of answered your own question. Since the ICM wire has continuity to the correct pin (no resistance at all?), but no voltage where there should be, it seems that wire is 'shorted' or 'touching' another wire.

Bad long term solution, but a good way to test: disconnect that pin from the ecu harness, and run a wire directly from the ecu to the distributor.

 

Yeah the only thing that I wonder is where else does that wire go? It uses two pins at the ECU (I think b15 and b17) and they both are continuous with the pin at the dizzy, so today I'm going to try hooking them both directly to the dizzy and bypassing the harness. I also am going to consult my manual and see where else that ICM wire goes, because this car was running when it was DPFI.

 

I ran the ICM wire directly to the dizzy and it still didn't get any voltage (the ecu is not putting out anything when it's in this car for some reason) What causes the ECU to send the ICM signal? What controls it? I've checked all the powers and grounds going into the ECU and they are all in order... I don't get this car it's killing me lol.


anyone?