RX7 RX-7 FC coil wiring

[riceandbeans]

MSI chipset, msns-e (not sure what version),MT 029j, V3.0 PCB
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As many of you may know, I'm doing a S4 13BT swap into an 85 RX-7 GS. I've managed to make just about everything work ignition-wise. The CAS signal conditions perfectly and pulls the 3 LEDs for coil events as it should.

However, the wire color codes of my coil/ignitors (the stock FC coils and ignitors) do NOT match anything I've found on any of the threads anywhere, so I'm not sure how to wire them up. I took off the plates for the ignitors and found the following letters stamped into the plastic casing of the sealed ignitor unit:

• LEADING COIL IGNITOR:

• stamping.......wire color
  B.......tan
  C.......black
  F........not connected

• TRAILING COIL IGNITOR:

• stamping.....wire color
  C1.........black
  TAC.......yellow
  CPU1....gray
  CI..........white
  ST..........red
  +B..........brown
  C2..........blue

(note how above wire colors do not correspond to muythaibxr's diagram seen here: http://www.rx7club.com/attachment.php?a ... tid=137993)


Could somebody inform me as to which of the above values correspond to "IGt-L" and "IGs-T, IGt-T, and IGf-T" for the leading and trailing coils, respectively? Also, what does one do with all the other extra ignitor wires that are not addressed as the "IG-x" type?

Thanks.

[renns]

Attached are pics of the two coilpacks on my bench.

The leading coil has three wire colours used, but only two make it to the connector. The black wire is only between the ignitor module and the coil -ve terminal. The brown wire is switched 12V supply to the coilpack, and the pink wire is IG-T Leading. On my ignitor, the letters 'Ig-t' are molded into the housing right beside that wire.

The trailing coil pack has a multitude of wire colours. The brown is again switched 12v. On my trailing coilpack a separate 2-pin connector just to provide power to the coils. The other connector is a 4-pin unit. The white and pink wires (4th and 5th from the left) are Ig-s and Ig-t.

Hope that helps a bit.
Roger.

[renns]

Here's the snippets from the FSM. If you don't have a copy of these already, send me an email and I'll forward them to you.

[riceandbeans]

Roger/all:

I went ahead and tried out the bench setup for the coils/ignitors, but don't seem to be getting a spark. I tried a 12V source from both a computer power supply (250W) and a lead/acid car battery with no results. I hooked up a spark plug to one of the two output ports on both the leading and trailing coils and observed the plug to see if visible spark was produced when I gave the MS an input rpm.

For the leading coil, I probed the IG-T wire from the MS with a sweeping-needle voltmeter and proceeded to "crank" the engine. I observed a fluctuation in voltage ranging from ~0-5V. Due to the inertia of the needle, I was unable to see this change accurately, but it looks like the IGT line is active to an extent.

If my IGT line shows signs of life, and the leading coil is receiving 12V, and the spark plug casing is properly grounded- is it reasonable to assume that the coil and/or ignitor is bad? Am I not hooking something up? (my coil/ignitor has two inputs- 12V switched and IGT, and one output- spark plug (which is grounded).)

Any help would be greatly appreciated.

[renns]

I went ahead and tried out the bench setup for the coils/ignitors, but don't seem to be getting a spark. I tried a 12V source from both a computer power supply (250W) and a lead/acid car battery with no results. I hooked up a spark plug to one of the two output ports on both the leading and trailing coils and observed the plug to see if visible spark was produced when I gave the MS an input rpm.

A few potential issues come to mind:

The leading coil is double-ended, so you need to have two plugs installed and grounded, or run ground wire to the other post during testing.

Did you configure the software properly for rotary ignition? You put pull-up resistors in place at the led's, and use the junction at the led as your output signal to the coil? Are the coilpacks grounded?

Roger.

[riceandbeans]

Roger:

The coilpacks themselves were not grounded. Do they ground through the casing of the ignitor/coil unit?

I did all the necessary MS rotary changes, and all the Q14-Q16 resistor pullup hardware modifications.

I tried this for both the leading and trailing coil assemblies (using only one spark plug and plug wire). Would I expect to see a spark out of the trailing unit, because it is not double-ended like the leading coil?

I think that my problem stems from the fact that my coilpacks were not grounded at all. I'll try grounding them when I get back from work.

[renns]

Roger:

The coilpacks themselves were not grounded. Do they ground through the casing of the ignitor/coil unit?

Therein lies your problem. Run a ground wire from each metal mounting tab back to ground, and I'll bet sparks will fly!

Would I expect to see a spark out of the trailing unit, because it is not double-ended like the leading coil?

The trailing unit needs to be grounded as well. If it's wired up correctly (Trig and Select connected), then it should spark as well.

Roger.

[riceandbeans]

Roger/all:

EDIT: 05/09/06

Symptoms: Leading coil would not fire at all. I think that's because I fried the ignitor when I mistakingly grounded a wire I shouldn't have, then observed smoke arising from the condensor unit.

Trailing coil #1 would fire normally, however, I couldn't get the plugs to alternate fire. I tested both trailing coils by switching plugs/plug wires and also the terminals on the coils themselves. All hardware, ignitor aside, was deemed as functional.

Just tonight, I got my hands on an oscilloscope (tektronix 466- booyah!) and probed the LED pullup circuit to find the following:

Q14: Leading coil trigger- seemed to be functioning as it should at all rpms, 0<x<1200rpm
Q15: Trailing coil select - would only pullup @ rpm > 770rpm, if rpm < 770rpm, the line would stay logic low.
Q16: Trailing coil trigger - again, would only pull up @ rpm > 770rpm.

Note: Even above 770rpm, Q15 and Q16 were not completely consistent on the scope. They often did not pull up correctly.

I tried messing around with R52/R56, starting at full anticlockwise rotation, then rotating clockwise by 360 degrees and testing @ ~300-700rpm until the resistance got to a point where the rpm would not register reliably on MT anymore. I saw no results in getting Q15 and Q16 to pullup correctly at rpms of less than 770rpm.

Help!