Black Knight RX7 FC3S

iTrader: (7)

From a continuation from here
https://www.rx7club.com/2nd-generation-specific-1986-1992-17/home-made-checker-light-tps-707352/

My trailing coils are not firing, BUT my tach works.

I have voltage at both primary terminals, so Im getting power from the wires.

The problem is that there is no spark coming from the secondary.

I used a small brake light lamp as a test light, and from what I see they both stay constantly on while cranking. Shouldnt one of the terminals be on and off. It gets the signal from the ECU right?and the ECU gets its signal from the CAS?


Im going to try and check if the MAF is alright.

HAILERS

Pull a Trail COIL wire out and just rest it in the bore. Start the engine. Pull that wire out of the coil bore about a 1/8 inch or so. I'd bet you see a good spark when you hold that wire just out of the bore of the coil.

http://www.teamfc3s.org/info/articles/demystifying.html

turbine

iTrader: (1)

you need power ground and signal. if you have all of these then your coil is bad. if you dont have signal the n check your crank angle sensor

Black Knight RX7 FC3S

iTrader: (7)

I did what you said and there is still no spark.

I had a bootless plug wire just "hanging" in the trailing coil and the other end where I had a spark plug on was at the strut tower bolt. The engine started and there is still no spark, Im moving the bootless end in and out of the trailing coil slowly and no spark. I tried it with another wire and still no spark.

I tested the CAS and the G terminals had 168ohms, and the NE terminals had 167 ohms, well within the 110-210 ohms spec. I tested the Coils and they are also within specs the Trailing 1 is .8ohms and the trailing 2 is .7 ohms.

I checked the wires on the ECU and its not burned or anything. Maybe if I check the continuity to see if there is a break in the wire somewhere........

turbine

iTrader: (1)

if i remember correctly your signal wire is the pink wire take a 12 v test light and pierce the wire then have an assistant crank the engine. your test light should flash.

Phantomkid

is the primary firing..i believe the ecu gets the cas signal and uses it to control both grounds. Looking at the wiring diagram, http://www.teamfc3s.org/main/factory...NG_DIAGRAM.pdf ,shows you should have power at both b/y wires..... i believe the trailing is grounded at its mount. good idea to clean the contacts i've heard of that problem before. but if it has power at both wires and is getting grounded from the ecu and has a good ground at the mount maybe you need a new trailing coil. If you have one end of your trailing light on the a ground and the other on L/Y, L/R, or BR/Y you should see the light turn on and off this would be the ecu working properly if you just see a steady light on then the ecu is not grounding as it should. Although i dont know which wire is the coil grounds. Good luck

Phantomkid

o as for making sure it has spark i usually pull the entire plug out just make sure the threads are grounded you can see the spark jump on the spark plug. make sure both arnt firing.

Black Knight RX7 FC3S

iTrader: (7)

The car runs, the primary is firing, just that the trailing isnt.
I dont under stand the color code from that manual......whats L/Y, L/R and BR/Y.
Y-Yellow R-red BR Brown?
Whats L

Im used to the three letter abbreviation.......

Phantomkid

l- im guessing is lilac/ purple on the fsm theres a chart tell your the colors

Phantomkid

haha i meant to edit this is and put it in the wrong line ....better then vw where the colors are abr. of german words so red ro and ge is yellow sw white.

Black Knight RX7 FC3S

iTrader: (7)

Well, theres no short in the wires leading ot the ECU.
I even checked the CAS wiring to the ECU to be sure. They all have continuity.
The ECU is grounded well. I took the stock grounding wire comming from the harness and spliced in a wire going through the firewall to the negative post of the battery. And even grounded the case.

Its a pinkish color, but at the connector its attached to the Blue/yellow stripe wire. You sure thats the signal wire? I used a light to test it and there was no light, I even tried at the ECU harness.

HAILERS

When you have everything hooked up, and the engine idling, does the tach work or not?

About the Trail coil/ignitor..........There should be 12 on the BLACK/YELLOW wires if the key is ON. Actally two black/yellow wires on a single connector.

The ignitor triggers when a ground is put on it from the ECU.

The trigger (ground) is sent out on pin 1X (blue/yellow).

The wire colors are in the wiring section of the free onlin FSM that can be downloaded from this site. See the FAQ secton.

BY is black/yellow
LY is blue/yellow
BrY is brown/yellow
LR is blue/red

The ECU can sit on a piece of foam and work. No chassis gnd needed. BUT the coil assy has to be grounded by at least one of it's hold down nuts. The ignitor in the assy gets its ground from the coil/ignitor chassis. Must be bolted down. Like I say, even one nut would do the job, so don't go thowing a bunch of extra gnd wires to the assy.

There's a single, black, bullet connector on that coil assy. That is a diagnostic plug and must never be put to ground.


So? Does the tach work or not.

Black Knight RX7 FC3S

iTrader: (7)

the tach works and there is 12 volts to the blk/yel wires with ign on
so im guessing the coils are bad.....

I'll see if I can get a signal again on the blu/yel wire again.

HAILERS

Now that's really odd. I always assumed if the trail coil was not sparking, then the tach signal would not be there, therefore the tach would not work. Normally that is the case. I'm lost then.

Maybe try two new TRAIL plugs. Maybe their bad. Or swap the trails and lead plugs and see what happens. Won't cost anything and you can swap them back.

Trail plug wires bad? Swap in some new or known good ones.

I'm stummped what with the tach working. I'll think about it.

The only good part of your problem is that the car should start and run using only the lead coil. There should be no noticable performance diff when driiving normally.

Black Knight RX7 FC3S

iTrader: (7)

I tried 3 different plug wires and the Trail coils still doesnt fire. I dont know about swapping the spark plugs itself since, if it doesnt spark when I put another spark plug on it and let it ground out to the engine or strut tower it doesnt spark.

This is the weirdest problem I ever came across on the rx7.....for any car for that matter.

If the car is in fail safe mode......that would not fire the trails right?
But my car feels fine through out the rev range.
I know the fail safe mode stops the trailing coils, but how bad of a performance hit is noticiable on a fail safe or limp mode car.

HAILERS

I'd try the FSM, Control Unit section.

There's three wires involved. All in the big plug.

1U is the Select signal as mentioned in the article I posted in another post. It determines which of the trail plugs fires. I put a meter on that wire at the ECU. Backprobed the plug. Key ON, engine off, it reads approx 4.5 volts. Turn the crank pulley by hand and that figure will change to zero volts at some point. Mostly it will be at 4.5vdc, then change to zero for a spell as you turn the crank by hand or use the alternator pulley to turn the engine.

1U will read approx 2.2 vdc with the engine at idle, 750 rpm. I read that on my meter also.

1M is the feedback signal. With the engine running it read approx 1.30 for me. Under 2vdc is what the FSM calls for.

1X.....frankly you KNOW 1X is good because that is what feeds the tachometer. I put a meter on mine and read Freq and it reads in freq twice what the actual rpms are. Normal. It should read below 0.8 vdc. Mine does also.

If the engine is running, and I lift the trail coil off it's mount, the tach stops working. And if I reinstall the coil assy with the engine still running the tach still does not work nor the coils. There's some sort of protection in the ECU I suppose. If I then turn the key OFF Iand then start the engine again, the tach and spark work normal.

I don't know. I think if a number one trail plug was not anygood at all, that might keep both from working. I'd try two OTHER plugs. Maybe some old lead or trail plugs.

I'd a swore if the tach worked, then there had to be spark. Mystery to me.

Black Knight RX7 FC3S

iTrader: (7)

Im going to do that tomorrow night.

So with the engine on the 1U will read 2.2 at idle, but with it off it will read 4.5.
Im just thinking now what might be the problem is there is no voltage on that wire. I took a light on the select signal wire yesterday, and it didnt lit up.
Though it might also be that I didnt probe it in hard enough to get a signal, I should try cutting the insulation off or something. I just hope that there is voltage on that wire.

BTW, do you know what the Feedback signal do.

HAILERS

****So with the engine on the 1U will read 2.2 at idle, but with it off it will read 4.5.
************************************************** ***************

Here's the deal. With the key ON, engine off, it will either read zero or 4.5vdc (on 1U).

IF you turn the enigne by hand, the reading will change. Say it was 4.5vdc. You now turn the engine and turn it for most of a revolution. It will change to read zero as you come to about (guessing) 20* BTDC.

It'll stay there at zero as you turn the engine, and the 4.5vdc will reappear somewhere around (guesstimate) 20* ATDC.

It's like that article mentioned. The trail ignitor sparks the T1 and T2 by either going high (4.5vdc) or low (0 vdc), on the SELECT signal. And the Select signal is that wire your looking at.

Again, I'm amazed you don't have spark, mostly because your tach is working and the tach gets it's input from 1X. Just odd.

I really don't understand why the voltage changes from 4.5 to zero at the particular place that it happens. It's definetly not AT the trail mark on the pulley when it changes. But if I start the engine and put a timing light on it, the T1 shows up where it should.

NOTE: Most of the time while rotating the engine by hand, the voltage will be 4.5vdc. It will turn to zero but stay zero only a small portion of the time that you turn the crank by hand.

That was done on a hot engine.

Black Knight RX7 FC3S

iTrader: (7)

heres an update.....all the wire voltages are the same as you did on yours.

*sigh*, this sucks.
I lifted the coils off the ground bracket and the tach does not work also unless I restart the car again.

I changed the trailing spark plugs with new ones and still no spark.....im stumped on this.
The only thing I can think of is that the coils themselves are bad. I guess I'll see if changing them works.

HAILERS

Seems so. Used ones off a na or turbo, series four or five will do. Maybe twenty bucks for the assy from the wrecker

Oh. I would not use a brake light bulb on any circuit that has anything to do with the ECU. Paranoid here........with reason. Use a LED type light if your going to use anything like that.

NZConvertible

Those colour codes should have a slash to indicate two colours, a main and a stripe, i.e. B/Y is black/yellow, L/Y is blue/yellow, Br/Y is brown/yellow and L/R is blue/red. Otherwise confusion reigns, e.g. GY is grey, G/Y is green with a yellow stripe; BR is brown, B/R is black with a red stripe.

HAILERS

Well. It depends. It depends on what FSM your using at a given time and whether there's a full moon out or not.

IF one has the GOOD FSM, the 87FSM, then the colors ARE, BY or LB or BW and NOT B/Y or L/B or B/W.

IF one is restricted by only having a 88 FSM on hand, then he has to resort to hackeyed lettering shown in that manual.

So I done did right after all. Eh? I'll attach a sample later (forces me to leave the laptop and easy chair to go to the desktop and scanner. What a pain.

EDITED: I already read your reply in the post below. I've an answer for that also.

And thanks for the input on the finding of TDC.

NZConvertible

And next year (and in all subsequent years) they fixed that confusing mistake so nobody else would ask why they can't find the "green/yellow" O2 sensor wire...

dean23

im having this same exact problem with my car... except i have a mirotech and aftermarket coils. everything is working and gets power except the trailing coils. ill be VERY interested on how you fix this problem.. i too have been stumped by it for quite some time..