no start problem, only sparks 1/3 CAS rotations
 

ok so im working on this FC that will not start or run. it has TII ecu, N/A harness (with the 3 wires cut to convert it to TII, including knock sensor addition), S4 N/A block. i unplug the CAS and spin it by hand, and the leading coil only sparks once every 3 rotations of the CAS, as does the injecotrs. Ive tried it on my brothers running FC, and it sparks a lot more often, seems to be about 4 spark/injector events every rotation.

Ive tried several different CAS, two different ECUs, and they all do the same thing. Ive checked continuity between ECU and the CAS and leading coil and its all good. im stumped?

sounds like you should grab an old plug and have some ank car as you watch for spark one at a time. pull the return fuel line, crank, and check for fuel, make sure you re stab the cas right. check fo 1k olms resistance between the green and black wire on the tps. 1 rotation the leading fires 6 times and the trailing 3.

if you have already replaced the cas with a different one and you have fuel and good timing tps try replacing the coil pack with a spare. i case you have not tried pull the egi fuse, if non of that works torch the plugs and try to start it

I started writing something probably 4 or 5 times, then realized I had ran into this exact same situation with another car. Check +12v and ground AT the ECU. Clean up all grounds, and do a voltage drop from each ground pin on the ECU to a good known ground on the chassis. If you're getting a voltage from an ECU ground wire to a real ground, then there's a high resistance connection somewhere along the ECU ground wire.

ive checked all the grounds.. they are all about 0.0-0.3 ohms at the ECU connectors. We have had 3-4 experienced rotary mechanics look at this car and we are all stumped. We have tried the following..

Checked all grounds
Checked for 12V at coil and ECU
tried 3 different CAS
tried 3 different ECU's
tried a different leading coil
tried 2 different engine harnesses
re-ran the shielded CAS cable, bypassing the harness

they all result in the same thing, it will spark only 1x per 3 rotations of the CAS. The thing is, it seems like an ECU problem, becuase not only does it spark only once, but you can hear the injectors firing also, so it cant be related to just the coils or coil harness

Bump this is my car we are having issues with heres the story i got an S4 TII as a project spent months figuring out why it was tying to start so hard. So i ended up pulling the motor out and swapping in an NA stage 2 street port and i have swapped the TII harness with an S4 NA harness now also installed a new starter, new plugs, new plug wires these are the only things i have changed since the TII swap. We have checked all the ground and the continuity and everything checks out. The weird thing is we didnt have a spark issue with the TII motor we have swapped 3 different ecu's, swapped 3 different CAS, 3 different sets of plugs and we have the same issue I have had the best rotary people in SC look at this thing and we have no clue someone please help

It's not 100% for sure there wasn't a spark issue with the original engine. There was only one confirmed start at which point there was an engine fire that required a new engine harness. When it was pulled for a rebuild the rear rotors and irons were severely rusted and thus the decision was made to use one of my spare engine's since it was just sitting on a shelf at the shop. As far as things that have been swapped and check or double checked. Everything in the engine bay has been replaced or is within spec. It's my opinion that it is something under the dash, but I don't have any way to confirm that until the dash is removed. i only mention that as a possibility because the car came with a spare chassis harness. Which to me always seemed somewhat odd since that's not something you just give to someone when you sell them a car. Please bear in mind that the car came as a half finished project that had for some reason sat unfinished for an unspecified amount of time.

This FC is a scooby doo mystery.....What we need is the Dr. House of RX7's to help us. I dont even thing the best rotary mechanic in the world could help at this time.

*think

If you don't have this fixed in 2 weeks, I may head up to take a look for myself. From what I can remember on the stock system (I now run a standalone), there are 2 signals from the CAS. One gives a pulse to the ECU 24 times (IIRC) every rotation, and the other signal is twice per rotation. There is one signal that just tells the ECU how fast the engine is spinning, and the other is a reference. It uses the 2 toothed signal to toggle the trailing coils, but fires the leading coil is wasted spark, so it fires both spark plugs 2x per rotation.

I'll have to think more about this issue and get back to you....

We ran the CAS independently to the ecu had the same problem the problem may be the wires.from the ecu to the Injectors and coils I don't know this car has stumped everyone

It's more than likely an issue with the wiring. If you have a set of coils, ecu, and CAS from a running car, it should be running by now. Inter-connecting wiring is probably the issue. Did you check the insulation resistance of the 4 CAS wires to ground, or even together to see if they're pinched and shorted out somewhere?

Everything has been checked except for under the dash..... I was hoping it wouldn't come to ripping out my dash because its in mint condition :(

Use a multimeter. Unplug the cas, unplug the ecu, measure continuity between wires, and wires to ground. Should all read "OL".

We have already done that ohmd everything checked all the voltage and continuity and it checked good but still get the same response 1/3 spark for every fill CAS rotation

Full

You may have proper continuity of wires, etc, but do you have the CAS wires and all other sensor/output wires going to the RIGHT places on the ECU connector?

Yes, i checked using the connector pinouts in the FSM. there is not much difference between N/A and turbo as far as ECU pinout, and no difference as far as coil outputs and CAS inputs

edit here are the differences..

Pin Function
1R power steering switch (NA), Knock control (Turbo)
2K split air solenoid (NA), twin scroll solenoid (Turbo)
3D A/T inhibitor switch (NA), fuel pump resistor relay (Turbo)

I've been taking the dash out to see if anything is wrong under there I'm half way done its a pain

I doubt you need to pull the dash out. There's really no reason for that. I know there's really a small difference between the NA and TII harnesses other than the extended/shortened wires here and there, and the 3 pins. I did this myself about 3 years ago, but ended up going complete standalone. The only reason I ask if you've ohmed them each to ground (input from CAS and outputs) and also wire-to-wire, is because I've seen it stump many people before.

Looking back, I didn't see anything about changing out the coils. They have the ignitors attached to them....

We have changed the coils 3 different times

Bump

AGreen,

I was part of the "party" on Saturday.

I ran the meter to each CAS wire individually on each end to verify they were in the going to the correct ECU pins. No issues found.

We also pulled the CAS from one of the cars that had been driven to his house to verify that we were dealing with a working CAS. No change.

As previously noted, we ran individual wires (shielded) from the CAS to the ECU. No change.

The car was hooked up to a battery charger/jump unit that was putting out a LOT of amps. I'm not sure if that could cause any amount of interference in any way. The battery is relocated to the rear hatch area, but I can't speak for the quality of the relocation.

The only oddity is that I noticed near the end of the day that I would occasionally see a faster bump on the tach. Instead of being a bump every couple of seconds, it would show one per second (roughly). Subsequent attempts would vary between these two variations.

cursed fc

Yeah cursed is right..... I don't really want to throw down q lot of cash for a stand alone unless someone can get me a really good deal on one but this FC is a pain 4 of the best rotor mechanics in SC can't figure it out so I doubt anyone else could unless its some off the wall shizz

a standalone ems is the only solution. FC wiring sucks

I've been operating under that theory for awhile now. For many reasons.
Yep. I agree with that 100%. Still better than the FD though.

Where are the grounding wires under the dash? And anyone know what wires go to the coils and Injectors?

Oh I have a wonderful Factory wiring diagram ... Mad rare and splindifferously complicated.

Four firings of one turn of the CAS is normal. Yours isn't.

Pull the CAS out of the engine and leave the elect plug on it.

Pull the small white, two wire connector off the Lead coil assy. Backprobe the black/yellow wire in that plug.

Turn the CAS by hand while watching the meter (key On, engine OFF). See how many 0-5 signals you see when turning one full turn. Matters not which direction you spin the CAS, same results.

Each time the meter goes from 0vdc to 5vdc you should get a firing and you should see that four times when doing this.

Let's say you see four trigger signals (5vdc shows up). Then it isn't the ECU or wiring or CAS as the problem, it's further downsteam i.e. coils assy.

On a series four car, the wires b/t the coils and the ECU are a straight shot with no connector inbetween at all. On a series five that is NOT the case.

MY guess is that those wires are ok. Now the CAS four wires have a connector b/t the CAS and the ECU. Make SURE this connector is in place and connected together properly and also ohm out the CAS wires from the ECU plug to the CAS plug and while there make sure none of those four wires is going to gnd (both ECU plug and CAS plugs disconnected doing so).

The plug that is inbetween the CAS and ECU is called FE-04 (front harness to engine harness)
and if memory serves is somewhere below the brake booster/master cylinder area.

Also answer this.................when you get in the car and stare at the tach needle.....does the tach needle make one bump upwards when the key is initially turned to just ON???? Should.

Series our TURBO EM harness in a NON TURBO car???? Yes or no. Yes from what I understand. How did you handle the alternator wiring if that is the case. How did you handle the boost sensor wiring that is different than the non turbo vs the turbo em harness?

Nothing wrong with stk Mazda RX wiring at all in general, if someone has not buggered up the connectors.

http://rx7.pw.cx/guides_manuals/coll...ystifying.html

******* Therefore, and this is important, in one eccentric shaft (crank) revolution, an ignition event occurs every 180 crank degrees.********

The above from the attachment in my other post above.

And we know the CAS rotates at 1/2 eccentric shaft speed............so in my mind four firing events with one full CAS rotation is normal and makes sense.

And just in case.........either of the coil assys MUST have at least one of their attach fasterners in place. The ignitor in each pack gets it's gnd from the body of the coil assy touching the chassis for a gnd point. Also the battery neg cable has a splice off it that attaches just at the base of the left front strut tower.This is the main CHASSIS gnd point on the car.

its not a ton of money to build a mega squirt. aaron has a write-up. also. maybe go crazy and run some grounds. id hit the fire wall, alt bracket, keg, maybe one on the frame somewhere. had a towncar once....kept blowing throttle cables...after the 3rd cable i figured out that the throttle cable was the best ground to the fire wall....from that day i hook up grounds everywhere. better safe than pissed.

Haliers,

The car is an S4 Turbo with an S4 NON-Turbo EM harness.

Ok. But remember that turbo and non turbo EM harness wiring does not match up unless steps are taken to make them match up.

And were the harnesses on the left side of the engine changed out for any reason?

Also..........on non turbo the alt wires are in the EM harness and on a Turbo car the alt wires are in the ENGINE harness on the left side of the engine. So the question is......is the two wire plug meant for the altenator in the EM harness connected to ANYTHING at all? That plug has one black/white wire and one white/black wire.

Grounds. The enemy of any FC owner. So if the CAS is verified good, the wiring has been replaced with the proper 4 wire shielded cable (I assume you properly grounded the shield), the ECU has been changed, the wiring to the coils is verified, changed out coils, I'd start with beefing up the ground wires. If that fails, then back probe EVERYTHING on the ecu with the key on. If there's a sensor that's shorted or something, it could be sending weird signals to the ecu. Maybe not even a sensor, but wiring going to a sensor could be shorting out. I've definitely seen some weird signals going through ecus, doing some crazy things to outputs because of a completely unrelated system.

The FSM does have a voltage pinout section for using the breakout box, but a multimeter works the exact same.... just a little slower. Do NOT use a test light, you'll blow stuff up inside the ecu. If you have one, use a logic probe, they're great.

Like I said, if it's not fixed by next weekend, I may be able to drop by and take a look.

-Green

OOOOPS. I made a big mistake in my posts above. I should have written to backprobe the small white two wire Lead coil plug and backprobe the GREEN/yELLOW wire in that plug NOT the black/yellow (batt voltage with key ON).

I feel the problem lies in the fact you have a non turbo EM harness mated with the Turbo Front harness. Need answers to questions posed in my other posts to try to help out.

The engine harness isn't the problem I just put in the NA harness last weekend because my s4 TII engine harness was doing the same thing so I thought changing it would fix it guess I not

I quote myself sometimes too :)

You have to answer questions posed to you to be helped.

Depressed bump

Ttt any other ideas?

Start unplugging sensors to see if you get spark when spinning the CAS. It really is worth a shot.

http://www.rotaryheads.com/PDF/2nd_g...tems_turbo.pdf

^Page 32 gives standard voltages for ecu pins.

Ttt REWARD first person to get her running gets $200 :)

Update now I have no spark when I spin the CAS

W/key to on, the Brown wire in the 3 wire TPS plug should have about 5 volts. Does yours?

Negative its a 4 wire clip black white red and green and I'm pretty sure its 2 signal wires and 2 grounds wires

My bad thought u meant CAS I don't have a tps on my UIM but that wouldn't effect the CAS and coils

I have spark again 1/3 CAS spins like before

I only have spark when my egi fuse is plugged in wo could it be an injector problem?

The EGI fuses supply power to the coils via the main relay, and the EGI fuses also supply power to the ECU which in turn supplys the trigger signal to the coil ignitors when the CAS signals to the ECU are correct.

EGI INJ fuse supplies power to the individual injectors and coil assys, just like the jpg I attached a number of threads ago show.

EGI COMP supplys power to the ECU and also the numerous solenoids on the engine.

The CAS signal to the ECU determines when each injector fires and when each coil fires.

Ttt all my voltages check out any other ideas?