Dead 1992 Eunos 1.6

[Mazda Mender]

Then it is the wiring from the ECU.
M-m

[nedski]

Have you pulled up the passenger carpet is it Wet ? The plug into the ECU corrodes also as well as the ECU out pins. I did one where i had to bypass the plug on a couple of pins and solder wires directly inside the ECU onto the board just behind the pins.
Just a thought anyway.

[dafeller]

Wiring from the ECU to what? I'm happy to dig into the loom. Should I start at the plugs?

BTW, the ECU is bone dry and the footwell shows almost no sign of any sort of corrosion or water intrusion. As I said, introduction of a new ECU didn't change things, so it must be something in the loom.

[nedski]

Ah yes just read you swapped them.

Does the rev counter flicker ?

edit..
So no spark and no fuel but it cranks over. I'm still thinking it's immobiliser. If it cuts them BOTH out not just one or the other.

edit 2
I think the ignition switch powers the starter and ECU seperately. So the switch is powering the starter so it cranks over but the ECU does nothing
not even diag. So using Spock logic somewhere between the ignition switch and ECU there is a power loss.
You may need to work out the ECU pin that should power it up and see if it's getting a live.

[nedski]

and maybe this diagram from google

http://www.miataturbo.net/attachments/m ... e-ms3x-jpg

[dafeller]

Thank you both for your suggestions. I am going to cut out the immobiliser tomorrow and see how it goes.

The Cobra 8510 has two immobilization circuits plus wiring into the ignition. On my installation, one of the two independent cutouts is wired dead-end into the ignition cut out, or the ECU cutout--I can't tell which--and the other is wired independently into another wire. The two wires in question are blue and black-with-a-blue-stripe, respectively.

I'm going to remove the immobiliser from the circuit with the dead-ended cutout, if that makes sense, hoping to kill two birds with one stone.

Does anybody know which is the wire from the ignition switch to the ECU?

[Mazda Mender]

The immobiliser will be cutting the power to the fault box that is why there is nothing, i still think it is the immobiliser at fault here.
M-m

[dafeller]

I've found the wiring diagrams for the ignition switch (in fact, the diagrams for ALL wiring in the MX-5 from 1990-2000) and the black and blue wire is the one going to the ECU. The blue wire goes to the ignition coil.

I will go home and remove the immobiliser from the black and blue line and see how she goes. If that doesn't solve it, I will remove it entirely.

BTW, the wiring diagrams are available here:

http://www.mediafire.com/download/mn1mz ... wiring.pdf

[flea]

Good luck fingers crossed

[dafeller]

Alright, I've now removed the entire immobiliser and nothing is any different. With the immobiliser removed, I have tried two different ECUs and still get no spark, no fuel and no diagnostic port action.

The only obvious thing about this situation is that the fuel pump will only work when a jumper is placed on the F/P pin of the diagnostic port, with the other end grounded. When asked to run via the open fuel circuit relay, the fuel pump makes no noise at all.

SOOOOOO . . .

I guess I should replace the open circuit relay (yellow one, under the dash) as it seems to not be working (although it worked in another car when we swapped it in the other day). Would some malady with the relay cause me also to have no spark, or just no fuel?

[dafeller]

VICTORY!!!

I wish I could say exactly what happened but I can't. After re-reading the whole thread, the only things I could think of doing were to disassemble the AFM and make sure that was good. It had some sloppiness in tow of the pin connections but I cleaned them up and there was no burn or short, so I buttoned it back up and reinstalled it. I then unplugged and replugged the ECU a couple of times, more to try to find the wiring so as to test and see if power was getting there or not. I never did check it, though, and just plugged it back in (the original ECU).

I then unfastened the fuse block inside the front left wing/engine bay and unplugged and re-inserts all of the plugs for the Fuel Injection Relay, etc. since an earlier poster had found a crack in his was causing problems. I took each fuse out and put it back in, checked the box itself, put it back in its mounting.

I then replugged everything else, put the jumper on the Diagnostic Port to work around the Fuel Circuit Opening Relay (which seemed to be a problem as the F|P would not be heard to run when I turned the key),

and up she fired!

I then removed the jumper for the F/P and it STILL started and ran. Over and over again, so the FP Opening Relay appears to be not a problem at all. I still can't hear the FP making noise when I turn the key, but it doesn't seem to matter.

I did have a leaky hose that I needed to adjust the clamp on, so I filled up the radiator and checked the oil and, well, she runs like she's supposed to.

The only causes i can think of are thus (1) dirty pin on a socket someplace, or (2) lose fuse connection on the bottom of the fuse box in the engine bay, (3) something about the AFM which is not understood.

The only obvious material change I made to the whole thing was to remove the immobiliser completely. I am going to put a new one in the car. Honestly, some of the non-starting after I removed the immobiliser could be up to not making sure everything was hooked up all at once; I was looking at so many things, I noticed one time I tried to start it without the ECU plugged in at all . . .

To show my confidence in the old girl, i'm going to get my partner from the rail station in an hour!

Thanks for all your help and discussion here. It kept me thinking and I understand my car much better now, even if I'm not quite sure what I did to get it running again!

[dafeller]

Anybody want to recommend a new immobiliser for me? I'm looking at Toad. I don't want to go with the same Cobra as I hate that little fob/T*t thing you have to use to deactivate it. The Toad has a proximity key which would make starting it much easier.

[flea]

Bloody well done. Nice to hear the good news

[Lazza]

AFM would make sense. I think, not sure but think, that if there is no signal from the AFM then the ECU won't fire fuel or spark i.e. if the ECU doesn't see airflow then it doesn't now the engine is running.

[Mazda Mender]

Great news , well done magic hands
M-m