[jonbill]

if, as you say, the spark plugs are sparking regularly and well but the timing light isn't flashing, you might want a new timing light.

[FWLRmusic]

We tested the timing light on another vehicle and it works fine. The spark plugs weren't necessarily firing regularly, I just was able to see a strong spark from cranking it over with the plug wire hovering over the intake manifold.

After some more research I think I might know what's going on.

Here's a photo I found on the internet of the 6G72 Crank Pulley.



Ours didn't have an adjustable distributor before we converted it over to the speeduino and I didn't notice those timing marks on the timing belt cover. I was under the impression that the big circle thing was TDC and was trying to get the timing set to that (which is in fact about 10 degrees ATDC by the looks of this picture).

I think the inconsistent timing light is from the rotor being in weird spots between the tips in the distributor cap due to our assumption of where TDC was.

Gonna test the theory tomorrow.

[jonbill]

Sorry, I hadn't read the thread properly
so - are the problems still the same with 24-1 wheel as you had with the 4g63 wheel? cylinders 1 and 4 aren't firing properly - is that right?

[FWLRmusic]

Well I've had lots of different issues LOL.

But now that we have the 24/1 wheel in, the problem is that the timing light just kind of randomly fires while we crank it over.

I really do think the rotor phasing combined with the discrepancy in the timing is causing the coil to fire when the rotor is not in the correct spot which in turn causes the spark to arc to different points in the cap... if that makes sense. Like the rotor is not right over one of the points, and therefore sometimes cross fires to a different point causing the timing light to go off randomly for any given plug.

[jonbill]

possible I suppose.
can you share the current tune?
Have you tried the timing light on all the cylinders? does it not flash consistently for any cylinder?

[PSIG]

For diagnostics, I would first disconnect the primary coil HV wire from the distributor cap and ground it, and pull the timing signal from that. It will fire the timing light on every cylinder, but you should see your correct timing every 3rd flash on a 6-cyl. If it is consistent in relative timing and is set correctly, that much is good.

From there I would verify rotor phasing (ignore the "bonus" stuff for your pattern) and plug wire placement for each cylinder. Assuming a clean cap (no carbon tracking or other issues), you should have clean firing to each plug and clean signals to your timing light. Let us know how that goes!

[FWLRmusic]

OK here's some new insight.

I've scoped the Cam, Crank, and Ignition Output from Speeduino, and the signal from the power transistor into the coil pack. Although the datalog shows a steady RPM (around 200), the ignition pulses are somewhat random which correlates to my issues.

Purple - crank
Green - cam
Blue - power transistor to coil pack
Yellow - ign #1 from speeduino to power transistor

Thoughts?






Tune: https://www.dropbox.com/s/r1gwvn0317t78 ... 2.msq?dl=0

[jonbill]

Whats the difference between blue and yellow? output from speeduino and input to coil sound like the same thing to me.

[FWLRmusic]

Ign 1 output (yellow) > power transistor (blue) > coil pack

[jonbill]

that still sounds like the same thing to me - aren't they just either end of a wire? , but never mind , its probably not important.
I'm not sure if the trigger pattern is configured properly - my head hurts
your tune says cam speed dual wheel with 12 primary and a single tooth secondary. but your oscilloscope plot shows 24 teeth between the single cam teeth.
so surely that's 24 primary and single tooth secondary?
what's the actual setup again? is the primary wheel on the crank or cam?