fd rx 7 wiring issue ? car won't start without switchon headlights
 

So I don't know if every FD has this or not but Do you guys have to turn on the knob to turn on the headlights to start the car? I was thinking maybe the wires for the headlights and ignition are wired together?

I’m not familiar with any known connection between those two.

What do you mean by “start” ? The stater doesn’t engage, or it cranks but the engine doesn’t start?

So when I put in my key and try to start it it will crank but it won't start until i turn on my headlights

This sounds like someone was in there before you, trying to "fix" things, and rerouted power for the EGI fuses through the Headlight relay. Does anything look out of place, with obvious signs of tampering? Look for missing harness tape, excessive tape, crimp connectors, etc.

where do i start checking? i started at the fuse box nothing seem to be out of place there check the wirng harness near around that area no problem also...

The first place I'd start looking is to test for continuity between the Headlight fuse and Start signal wire. This is a Japanese Series 7 FD, correct? VIN would begin with FD3S-4xxxxx, production date of 12/1995 to 12/1998. Have you tried pulling the 30A HEAD fuse and seeing if it behaves differently? That fuse feeds two terminals on the Headlight Relay, one of the power pins and one of the coil pins (call them pin 30 and 86 for simplicity here). The Headlight Switch supplies a Ground to the other side of the coil (pin 85), and the last terminal (87) goes to the Dimmer Switch to choose between high and low beam.

Also, may sound like a dumb question, but is yours an auto or manual transmission? The diagrams are slightly different for an auto vs a manual. In the Starter diagram, it's one more splice onto the Start Signal wire from the ignition switch, going to the EC-AT Control Unit for automatics.

so I pulled the EGI fuse and found that headlights still works but my Power FC stopped working ECU problem then?

and yeah i doo have a 1996 series 7

That's normal, EGI Fuse is ECU Power. No power=no fuel injected, so no start. Useful for de-flooding. Try pulling the HEAD Fuse and see if the car starts or behaves differently.

sorry for reviving this thread, but yeah. I'm trying to rewire the ignition from the headlight switch to the normal key on position, and i don't know where to start. would i do it from the EGI fuse to the key on position? or from the ECU ignition PIN to the ignition switch on position?

Oh yeah, I am not getting any power from the ecu when i turn to the key on position (headlight switch low beam at the moment) I did check the main relay to see if that is the problem why im not getting power but the relay is good. (I swap the other relay with the main relay to see if it would behave differently but it's the same, also i check the relay itself) checked all the fuses near the pedals fuses in the engine compartment everything seems good)

also if i switch the headlight and it works doesn't that mean I'm getting power from the fuse box. also the lights like Hazard and signal light are working, horn works too. that mean I'm getting power from the engine fuse box to the interior fuse box. NO? i honestly don't know where to check next for the ignition to give power to the ecu.

Collectively your 3 posts do not clearly describe what your problem is or what you're trying to do. Make a new thread to get better help