Testing Of Ecu Ignition Outputs

[nizm0zed]

Well, its been a long time since i was logged in here and on reflection my user name now looks pretty dumb...
Oh well...

So, i have a RB25DE in a 260Z coupe. (R33 S1 VCT, factory ECU and wiring loom)
It runs, rough.
At first i thought it was the usual coil pack issue, so i researched it and tested my coilpacks. the results said they were in spec but others had done the same with the same results as i was measuring and still turned out to be a dud pack.
I had a brand new AU falcon coilpack and leads from the old L28ET setup that used to be in the car, so i thought i would change that over and wire the AU coil in, instead of spending money to buy some more coils. Seemed sensible seeing as i already had all the bits i needed.
Fastforward a bit, the AU coil pack mounted in nicely, shortened down my leads so they look schmick, wired it up so it'd trigger using the ignition module.
The rough running and lack of power didnt go away...
I pulled the leads while idling and through the sound of the spark and lack of temperature in the exhaust runners, i deduced that no.s 4 and 6 cylinders werent sparking (well, they were because its wasted spark now, but they werent sparking at the right time)
I moved from there to assume that the Ignition module had failed internally on 2 channels and ordered a second hand one off ebay.
It arrived today and i just tried it.
Unfortunately the problem in no.s 4 and 6 cylinder still remain.

So, i am now at the conclusion that there is a fault at either the ECU (ignition trigger outputs) or the wiring inbetween.
The wiring is simple to test for continuity and i will be doing that, however i dont anticipate any issues there.
What i am really looking for is a way to test the ignition outputs to determine if i need a new ECU or not.

Is there any way to build a simple test light i can attach inline of each channel wire? eg a LED
How does the ECU trigger the ignition? Is it constant powered back to the ECU, with the trigger being a momentary break of the ground path? or the other way around, with the ECU grounding the ignition module to fire the appropriate channel?

I dont have an oscilliscope, nor can i afford one, dont know anyone with one, so im looking for some way to establish the condition of the ECU before spending lots of cash i dont have.

Any suggestions would be awesome!

[White GTS-T]

The ecu switches the earth to fire the coilpacks. To test it, you need to get yourself a noid light or an LED test light.

Good luck.

[nizm0zed]

lol, thanks for wishing me luck, i think im going to need it...

So, i'll rig up a LED to sit inline on each channel wire, it should pulse to indicate a signal, correct?
now to hunt through my scrap electronics parts, i know i have some bits somewhere...

[White GTS-T]

Correct.

[nizm0zed]

I just got back from testing every damn thing i can think of, and im f**king stumped.

I made a dodgy LED noid light. I used it to verify the ECU switching signal on each channel on both sides of the ignition coil.
All channels are good.
I tested the resistance of each trigger wire from the ECU to the ignition module, .2-.3 ohms on each wire.
I tested the resistance of each trigger wire from the Ignition module to the coil, .1-.2 ohms on each wire.
I tested the primary coil resistance, its within spec at .6 ohms on each primary winding
I tested the secondary coil resistance, its within spec at 9.2K ohms on each secondary winding.
I ran the engine in complete darkness, i cant see any cross sparking between leads.

No matter what test i can think of i have done it and it tests fine.
This engine should in theory be purring like a kitten, but its misfiring on cyls 4 and 6
The only thing i havent tested (thinking about it now) is the leads, i'll test them tomorrow, however i have already swapped no.6 lead previously with no change.

FUUUUUUUUU!!!!!!!!!!!! Its driving me mental!!!!!

[White GTS-T]

So when you lift the lead of cylinder No. 4 or 6 you can see/hear the spark, is it a bright white and crisp cracking? Have you got any photos of how you wired it up? Are you sure it's spark related?

[nizm0zed]

when i pull the lead off cyl's 2 and 5 you can hear it sparking regularly and quite quickly. (the idle also drops)
Any other cylinder and it sparks about half as fast.
If i pull the lead off cyl 1 and 3, you can hear the slow sparking and the idle drops.
Now, this is important because its now a waste spark setup, so paired plugs fire at the same time.
eg, 1 and 6, 2 and 5, 3 and 4.
So, from there i have learned that coil pack 1-6 and 3-4 are only firing every second time, where as 2-5 is firing every time.
The sound difference is quite distinct. I can also see the spark, however i cant visually see if there is a difference in spark intensity when i do that.
using an IR heat gun on the extractors i can see a significantly lower temp on runner 4 and 6, indicating that the cylinder isnt burning any fuel.
That leads me to the conclusion that the coil isnt triggering on the cylinder pulse.

Sure its not injectors you say? (now that i think about it myself i need to verify 100% to be sure)
You can hear the popping off through the exhaust as the unburned fuel is pumped out the exhaust and combusts as it mixes with the burning gasses later on
(which i guess is a good thing as it indicates that my extractors are scavenging quite nicely)

Edited December 16, 2013 by Satan_ate_my_jesus_fish

[White GTS-T]

A quick Google search yielded this,does this help?

http://wiki.r31skylineclub.com/index.php?title=AU_Falcon_Coilpacks_Conversion_For_RB20

Edited December 16, 2013 by White GTS-T

[nizm0zed]

yup, thats the wiki page i followed to wire it up, its exactly the same.

[White GTS-T]

So you've tried two igniter modules and it's the same with both?

[nizm0zed]

yup, both modules the same issue.
I tested the leads, all ok.
I swapped the wiring and leads so i could run coilpack 2-5 on cylinders 1-6, The thinking being that if the spark issue moved cylinders it was definitely the coilpack. Still the same cyl's not firing...

I checked and set the CAS/ignition timing. smack on 15 degrees.
Set the TPS, even got the idle sort of close to where its supposed to be.
Checked the injectors, they are all firing correctly (haven't done a flowtest on them, but that means pulling them out and $$$$)

i am now at the point where i will confidently say the whole ignition system is 100%, excluding the coilpack (90% confidence) and the ECU (90% confidence)
So, im going to find a spare ECU i can try before i spend more cash...