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