At my wits end... ANY IDEAS? LS3 with 24X trigger.

[nathaninwa]

There is also those little green arrows on the top of the tables that can be exported/imported

If you need to rescale the break points on the table without changing it, click on the double arrow on the lower left corner

[DLRacing]

OK, I installed the new LS2 truck coils. I ordered new harnesses, but of course the lengths were all wrong, and they had the LS1 coil connectors.
Fortunately, the AC/Delco coils came with pigtails, so I redid the harnesses to work.
I triple checked all the wiring, and ran the individual coil test to verify correct firing order.
Also reran the injector test as well.

I set the cranking dwell and nominal dwell to 3.0ms, and cranking advance to 0deg to be safe, and tried to start it.
The blasted thing STILL KICKS BACK! Exactly the same as with the old coils.

I looked at the log and I didn't see anything apparent, so I reset crank adv to -10deg.
It fired and ran for a few seconds, but when I tried to restart it a couple times, it again kicked back. I'm surprised it hasn't trashed my new starter yet.

I'm running out of ideas. With this being my first experience with MS, I just don't know where to look next.

I've thought about pulling the ign. fuse and cranking it with fuel only but no spark, to see if it's firing on compression, but don't want to flood it either.
Also, it's never done this with the old LS1 PCM, so I really don't think it's an internal engine problem.

Tune and logs attached. I hope someone can help.

Also, does anyone know an accomplished Megasquirt tuner in the central VA area, who could stop by and take a look?
I really need to get this thing at least driveable, so I can move it out of my bay, as I have a new race car coming soon.
If I can get it on the road, I want to learn as much about the tuning process as I can, before I eventually have it dyno-tuned.

Thanks,
David

[CRSTune]

Where in VA?

[billr]

Forgive me if this has already been asked-and-answered, but it has been a long thread...

Have you verified cranking advance with a simple light, on all cylinders? Is the sparking consistently at the same point, always, no occasional "flyers" or missed sparks (light flashes)?

[CRSTune]

This is what I saw based on the logs.

In the second log, the dwell reading matches what I'd expect it to be based on the battery voltage. For example, a cranking dwell of 3ms and a 36% correction at 10V so I get a dwell of 4.1ms in the logs. That's good.

On your first log, at 10V, I instead get a reading of 5.4ms. That's not even close. Even at max correction of 80% at 6V, the maximum dwell I should see is 5.4ms and yet the max in the log is 5.7ms. That makes no sense and I don't know why.

Based on that, this is what I would do. Reload the firmware. Load a 24x base map. Save the map you were using but don't use it. Set your dwell at 2.5ms with a 0deg cranking advance and see what it does. Of course, please log the attempt.

[gjestico]

Did you run another composite tooth log after you fixed the cam sensor ?

[nathaninwa]

Im not convinced it coil dwell at all. I just looked at a log when I changed out injectros and cranked on it a bit. Voltage dropped to 8.8 volts, cranked at 103rpm and cranking dwell corrected to 10.8 and it fired up

[DLRacing]

Forgot to mention, I've had this error a couple times when I open Tunerstudio.

"1 Warnings:
Warning: cranktaper_time row:5, col:0, One or more value higher than maximum: 25.3, Set to the maximum value: 15.0"

I'm guessing this is related to injector pw and not ignition.

This is what I saw based on the logs.

In the second log, the dwell reading matches what I'd expect it to be based on the battery voltage. For example, a cranking dwell of 3ms and a 36% correction at 10V so I get a dwell of 4.1ms in the logs. That's good.

On your first log, at 10V, I instead get a reading of 5.4ms. That's not even close. Even at max correction of 80% at 6V, the maximum dwell I should see is 5.4ms and yet the max in the log is 5.7ms. That makes no sense and I don't know why.

Based on that, this is what I would do. Reload the firmware. Load a 24x base map. Save the map you were using but don't use it. Set your dwell at 2.5ms with a 0deg cranking advance and see what it does. Of course, please log the attempt.

Will do.
Where should I go to make sure I have the latest firmware?

Hopefully I'll get a little time tomorrow after work to try your suggestions.

Thanks again,
David

[DLRacing]

Forgive me if this has already been asked-and-answered, but it has been a long thread...

Have you verified cranking advance with a simple light, on all cylinders? Is the sparking consistently at the same point, always, no occasional "flyers" or missed sparks (light flashes)?

I did that on the original coils, both cranking and running, and it was spot-on.
My damper is only marked for 55 degrees, so I couldn't check each cylinder. I'll get some timing tape when I get the chance.
Couldn't do it with the new coils tonight, as I was working on it alone.

[DLRacing]

Im not convinced it coil dwell at all. I just looked at a log when I changed out injectros and cranked on it a bit. Voltage dropped to 8.8 volts, cranked at 103rpm and cranking dwell corrected to 10.8 and it fired up

What coils are you running?

[CRSTune]

http://www.msextra.com/downloads/

Though I'd probably just use the firmware you're currently using. Then you don't have to worry about converting your MSQ. I'd update to the latest version after you have the problem fixed.

[nathaninwa]

Heat sync truck coils on my LS and and 2jz car. Have never had a starting issues with either

[DLRacing]

Did you run another composite tooth log after you fixed the cam sensor ?

I believe I did, but not sure which file it is.
If I get back on it tomorrow I'll do that, but I'm not having any sync errors, so I believe the trigger signals are good.

[CRSTune]

I've also worked with LQ9 truck coils before and never had a kickback related issue with them like the OP. But right now, I don't see any other leads.

[gjestico]

Did some more reading, and it seems that since the 24X reluctor does not have a missing tooth as such, the cam sensor is required for the engine to run at all.
The signal from my crank sensor looks really clean, and I can see the 24 distinct pulses in a repeating pattern, so I feel good that that one is wired correctly. (Can't get to it without removing the starter.)
I'm going to re-check the wiring on my cam sensor now, as that signal looks all funky on the composite log.

This is your older post. You never reran the comp log after discovering your incorrectly wired cam sensor I think ?. The fact is that the MS2/3 can run on just the 24x wheel with no cam sensor. The wheel may not have a "missing tooth" but it has an irregular series of tooth widths that can be read to the same effect as such.
It will be "wasted spark" and batch fire I think. Many an LS motor is running this setup with no cam sensor usage.
I am wondering if your cam sensor is doing something wonky. Thus the suggestion that you try the waste spark setup and disconnect the cam sensor.

[gjestico]

BTW the stock GM LS ECU, Is able to run the engine without a cam sensor. This is a failsafe built in by GM to reduce dead vehicle strandings. Its much better to have the customer able to "Limp Home" with the MIL light on than having to call a towtruck. It's remotely possible the engine was in this situation when it was running with the 411 ECU originally.

[nathaninwa]

Yes, I've suggested wasted spark and wasted fuel as a trial.

[DLRacing]

I believe I tried that before I found the miswired cam sensor.
I'll give it another shot though.

Thanks,
David

[nathaninwa]

What if it's a week crank signal and it needs 12v for this Ecu to operate correctly?

[DLRacing]

What if it's a week crank signal and it needs 12v for this Ecu to operate correctly?

If that's the case, the composite and tooth log should indicate that.