RotaMan99

I am working on a rx7 for a buddy of mine doing a S5 mani swap. Did the swap before with no issues.

I started on it monday and its been one maintenance issue after another.

Well, after putting everything back on and start the engine, I find there is no tach and the trailing coil is dead. I don't have my meter with me at the moment so I can't check for power at the coil or at the ECU or anything which is a bummer. This also means the VDI and AUX are not working as well, power cuts off at, im going to guess around 4000, this is going by what speed im at in which gear.

I checked the grounds on the engine since I did remove those but they are fine. I never touched the trailing coil or its harness.

I have never seen the TPS in my 88 effect the trailing coil but if I had the BR/W and BR/B (FSM says B) wire switched, could that cause an issue?

Also, the rpm signal wire at the ECU pin 1X (Coil with Igniter IGT-T Ignition Timing Signal). I tapped off of this for the 2 rpm switches I installed at the ECU but the wires are soldered together so thre shouldn't be a break. If this wire is infact OPEN as in disconnected, will this cause the trailing to not work?

misterstyx69

iTrader: (142)

If the Plugs are Bad on the Trailing "side",then the Tach does not see signal..so check plugs,and Wires,also the Trailing Coil.I would take a Wire Off at the Coil(Plug wire)..first to see if the Coil is Firing to the wire.(you wil get shocked..use Insulation!)..the coil should give off a "good Spark" to the Wire,that you can SEE...do that on one Plug wire at the coil,then replace and Do the Other wire..I found my Sputter problem that way..was a Bad Coil,on ONE side of the trailing coil.It may not Be exactly the Reply that you are Looking for(ECU).but it will establish if the Trailing is Firing.

RotaMan99

Im going to check the plugs. I suppose they could be fouled. Both wires don't fire, I already pulled them off which is how I determined the coil was not firing.

I appriciate the reply. Im hoping that maybe I just made a bad connection on pin 1X.

RotaMan99

I did some metering and found on on wire, 1X to be 5-7v when its supposed to be .80v. I can't figure out why, im going to try 2 things and see if it works, I checked all the grounds, wiring harness and such, checked the voltage at the ECU for the CAS and that was good.

Im almost out of ideas.

RotaMan99

So I can't find any shorts. I get power to the coils, voltage from the ECU gets to the coils, CAS voltage at the ECU is good as well.

The car is back in the owners hands but im going to have him check a few more wires on the ECU. I have a feeling the earlier short I was having problems with near the TPS connector or atleast in that section of harness might be the problem.

RotaMan99

So I got the car back so I can get the trailing side ignition working along with a bunch of additions to the car and engine.

I did some more troubleshooting on the trailing side and I made a spread sheet of the results linked below.
The Vehicle in question is Carlos' Rx7. My Ignition system works fine.

http://midnightgray.net/ignition.htm

Just to recap, I have tried a working coil from my car. I have also tried a working ECU from my car.

I am going to swap out the CAS shortly even though it seems to have checked out.

I removed the plug wires from the coils, if they work, I should hear the sparks arcing across like it does on my car easily.

Any Ideas? Hailers could you chime in a bit too? I know you were helping us over on TeamFC but I got a little more organized info now.

Thanks,
Justin

RotaMan99

I swapped out some parts once again to refresh my memory.

CAS, COIL and Some resistor under the trailing assembly. Don't know if it has any relevence to the ignition but I swapped it out anyways.

I performed a continuity test on the ECU grounds on both cars and got some interesting results.

I updated the spreed sheet as well with the results.

On Carlos' car. (car in question)

3G - 15.8 Ohms
3A - 20.0 Ohms
2R - 20.6 Ohms
2C - 17.3 Ohms

My car

3G - 1.0 Ohms
3A - 1.0 Ohms
2R - 1.0 Ohms
2C - 1.0 Ohms

RotaMan99

I did the ECU Ground test again and found that only with the ignition on do I get hign resistance numbers. With the ignition off I get real low numbers. 0.80 Ohms.

danegerous

iTrader: (10)

I know this is a documented problem man, maybe the guru's are asleep or something right now.

My friend's had the same thing going on and his starter wouldn't even kick over while the car had a new battery.

I wish I could be more help but maybe PM a well known mech on here or check the archive on teamfc3s.

RotaMan99

THe archives at TeamFC have nothng good for me.

The problem with this issue is that the answer is not documented at all. I remember a few people that had similar issues where the ECU will turn OFF the trailing side ignition but can't find the reason for it.

I was thinking of PMing Hailers and Icemark after I get some more information and have done some good testing.

danegerous

iTrader: (10)

I'm pretty sure I read up on it before, be it here or fc3s. Regardless I think you're better off messaging someone more knowledgable. I'd bet me lunch money that, it's an easy fix and it's probably something you over looked. Thats just how these things tend to be

RotaMan99

Well this one made me feel stupid but at the same time I had no idea this was possibility....

I first disconnected the front harness connector from the ECU and from the ignition coil just to see if there was power back feeding into the wire from some where... DING DING DING! I got 12v right off the bat on the wire that has both ends disconnected.

Well, the only electronic device on that wire is the 2 RPM switches that I installed. I tested both of them and they were both inputing power onto that wire. 12v from one switch and 8v from the other switch. I tested another MSD RPM switch in my car at I got 7v from the white tach wire.

The weird thing is that I disconnected these switches before when I first had the car back in October 2007 to see if they were the cause but the trailing still did not work. Maybe that was a seporate issue that is now hidding untill later. This is why I didn't think it was the switches untill now.

I didn't ever think it was possible for these switches to back feed power. I thought the white wire from the switch was only an input thus not outputing power. I was very wrong.

I now have to figure out how im going to run a new wire from around the tachometer in the dash down to the ECU if I can't find another tach wire, so I can power the 2 switches installed next to the ECU.

I automatically thought that pin 1X would be good for getting the tach signal since this is where you can hook up your Apexi SAFC and be fine.

I was also thinking of using a Diode on the tach input wires from Pin 1X so power would only flow one direction. I don't know how well this would work and I think its better off eliminating the potential issue all together.

Rotary_Powerd

Excellent use of diagrams. One has to appreciate proper illustrations

RotaMan99

Wiring diagrams work great! BTW, I have edited OEM wiring diagrams to fit your vehical so you could say that you have "custom" wiring diagrams for your car. hehe.

Rotary_Powerd

Awesome! Your the man bro!