'95 Miata ignition/timing assistance please!

Kevin Butler · **Posted:** Sun Jan 29, 2006 12:28 pm

Ok,

Basically I've got a '95 Miata in a '93 shell - '95 wiring, '95 ECU & '95 motor, all stock components. Mechanical timing is spot on. The harness in the car has recieved a little repair from wreck damage. I had to solder several splices in to repair cuts. All splices were sealed/insulated with shrink tubing.

When I go to fire the engine, it starts and revs up, then ceases to run. It feels like the fuel and ignition cut out. Additionally, I observed that the tach is not registering when an attempt to start is made.

Diagnostic codes are 1 and 3. According to Miata.net, code 1 is Ignition Pulse and code 3 is G Signal. For the best I can figure, that means check the coils and CAS(crank angle sensor).

Before blaming components, I checked the circuitry from the ECU to the ignition coils and the CAS - all good. I pulled the harness out to where I could inspect it(especially in the repair area). No cuts or chafing spots have been found yet.

I have a '93 manual, but it's not much good for this issue. Ignitors were incorporated into the coils after '93 as well as the CAS.

Miata.net doesn't really have any specific offerings on how to test components. They just say "its your CAS" or "its your ignition coils". Pretty useless offerings really, and both components are quite pricey.

So does anyone know how to test a '95 ignition coil and CAS with an ohm meter?

Thanks in advance for assistance provided.

Ashraf Farrag · **Posted:** Sun Jan 29, 2006 4:02 pm

Kevin,

It really sounded like an AFM problem if didn't mention the check engine codes. Have you cleared the codes and made sure the same codes are being repeated after resetting the ECU (pull negative terminal, push brakes)?

Did you repair any of the ignition pickup (CAS) wiring? It is usually shielded, so your repairs should take that into account.

Do you see RPMS on the tach when cranking? No RPMS means no tach (CAS) signal.

The internal parts of the CAS were changed from the 1.6L to the 1.8L cars...from an optical disc to an inductive style. IIRC, Randy Stocker's site covers this info and you may be able to get some test procedures for a similar design CAS (the Megasquirt folks I hear have hooked them up to a drill and watch for the triggers on an oscilloscope). I'm not at home, so my '94 FSM isn't handy, but I think it should give some voltages for the CAS...

Best of luck,
--Ashraf

RobLupella · **Posted:** Sun Jan 29, 2006 6:16 pm

Another AFM gone to hell :wink:

Kevin Butler · **Posted:** Sun Jan 29, 2006 7:23 pm

It' not the AFM. Having in effect two '95s, I switched the air boxes. The one I've been trying to use in the transplant works fine in my R package.

I took the ohm meter and checked for continuity across the 4 pins on the transplanted 1.8 CAS. I got partial continuity across the 2 outside pins. Compared those results to my '95 R package. No continuity across any of the pins. I performed a similar check on the 1.6 CAS - no continuity across any of its pins(the 1.6 had been running fine at the time of removal). Hmmm, Best 2 outa 3?

I took the transplanted 1.8 CAS apart. It has 2 Hall Effect sensors with a pair of metal blades rotating by them for signal generation. Like on Randy Stocker's site for 95.5 to 97 Miatas. I took the 1.6 CAS apart. It had the same exact Hall Effect system as the 1.8. The 1.6 CAS is from a '93 car. Hmmm, again!

The 1.6 CAS is too long to fit in the '93 body with the '95 engine. You can't fit it between the end of the head and the firewall. The plastic "circuit board" the Hall Effect senors are mounted to also has the plug molded in it and is secured in the CAS housing by 3 screws. It is removable. So...I took the board from the 1.6 CAS and mounted it in the 1.8 donor CAS housing. You can't install the CAS 180 deg out of phase 'cause one blade is thicker than the other. It's what we refer to as "pokey yoked" where I work at. There's only one way it can be assembled.

Tried firing the car again. Again, the same initial fire up with immediate kill. However, where I was originally getting codes 1 and 3, I now get (edited)code 1 only(gnd/10 jumper was loose). Also, still no tach registration.

Things to check next - AFM wiring(not part of repair work). (edited)I think the CAS problem is solved with the disappearance of code 3. (edited) I still would like to know how to check the ignition coils. I think they are my remaining hurdle. I am reluctant to start swapping parts from a running car to a problem car. I would hate to wind up with 2 non-running cars. Tomorrow I order a '95 service manual.

Still open for suggestions.

KB

Kevin Butler · **Posted:** Mon Jan 30, 2006 9:50 pm

Last nite, I swapped the air boxes with my R package. Fired right up! Tonite I swapped the ignition coils. R package fired right up. I've got 12V at the blue wire feeding the ignition coils, so that rules out the ignition switch, ya? I'm pretty sure the TPS is working. When you have the 10/Gnd jumpered the fan is supposed to come on when you move the throttle and it does!

Still got Code 1. The CAS transplant I made yesterday made the Code 3 go away.

Does any one have a '94-'95 Miata shop manual? I called Mazda Motorsports and they said the program they order them through has been down forever and there's no telling when I'd get a manual.

What feeds the tach signal? I've got no tach registering on fire up. I think if I could ID and resolve that issue, I might get somewhere. I currently have the '93 dash pod hooked up. Don't really see where that would be an issue, but what do I know? (Apparently not too much!)

:banghead:

Vincent Keene · **Posted:** Tue Jan 31, 2006 9:22 am

Kevin Butler wrote:

What feeds the tach signal? I've got no tach registering on fire up.

The tach signal generally comes from the (-) side of the ignition coil.

Kevin Butler · **Posted:** Tue Jan 31, 2006 11:52 pm

Its ALIVE!! Its ALIVE!! MWahahahahaha, MWahahahahaha! :eek:

You guys probably won't believe this but the car's been fine all along. It just wouldn't run without the proper ECU installed.

Ok, two '95 cars. One has an ECU labeled BPL9 in both large and small text on the one label. The other ECU is labeled BPL9 in large text and BPL9B in small text. The BPL9B is the ECU from Bad Kahrma. For fabrication reasons I swapped it into my R package when I installed the roll bar.

My R package car is an early '95 build. Bad Kahrma was a late '95 build. For late '95 builds, Mazda started sneaking in '96 engines and different wiring. Tonite, I had plans to chase a particular wire down for a short. The problem is, it wasn't there! Instead of having 4 wires going to each coil, this transplant motor has only 3. I found the ignition configuration I had to work with in the '96 wiring schematics. Then it all started to click.

Put the wiring back together, yanked Bad Kahrma's ECU out of the R, installed in the '93 and voila! Purrs like a kitten. I'll have this car at VIR Full yet.

:redcool:

Todd Breakey · **Posted:** Wed Feb 01, 2006 10:28 pm

Congrats Kevin!!! :beerbuds:

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'95 Miata ignition/timing assistance please!

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