MS3 + MSD6AL

[warlock.da.newbie]

Hello All.

I'm working out an issue with trigging an older (1997 date range) MSD 6al and am looking for a couple of suggestions. Currently I can start the vehicle but I see the RPM signal appears to be picking up interference. I currently have about 8 inches of unshielded wire coming from the distributor going to a weatherpack connector before I move to a shielded cable that is approximately 20 inches long. The cable shield is grounded at the distributor side to the intake manifold's distributor hold down bolt.
I am assuming trying to shorten the unshielded wire as much is possible would be a good starting location. Second is my grounding location choice a good choice or should I move to grounding my shielding on the MegaSquirt side? Finally, should I just start adjusting the MS3X's VR sensor filters to see if I can tune out the noise? Any other suggestions for working through my problem are more than welcome.

[billr]

Move the shield ground to one of the MS ground pins, leave the dizzy end of the shield floating.

[warlock.da.newbie]

Billr,

I haven't been able to get a data log but a quick 30 second run appears to have solved the issue. I believe my noise source was a old cap and rotor. I will go ahead and update again once I am certain I have the issue resolved.

Sean

[warlock.da.newbie]

OK, cap and rotor replaced which did appear to help with potential noise output. I was able to rewire my grounding so that the orange/black wire is wired to the MS3 pin 24 and the violet/black is wired to MS3 pin 1. The shield ground is wired to MS3 pin 2. While cranking I am getting the attached composite log. RPM appears to be extremely low then climb fast to the rev limiter then fall back low.

[billr]

I could not open that comp log, but would rather look at a run log (MSL) anyway. Is there a specific problem you are asking about? It will help if you reference specific times in the MSL and which data fields are of concern.

[warlock.da.newbie]

Here is the second composite log output that I had. I confirmed I am unable to open the log file as well but this second log file does open.

My main problem is I am not getting a valid enough RPM signal for the computer to try to even fire the spark plugs.

[Matt Cramer]

Try running both the regular data logger and the tooth logger at the same time.

[warlock.da.newbie]

Try running both the regular data logger and the tooth logger at the same time.

Matt,

Am I assuming correctly that this would be the composite logger and the tooth logger or are you looking for the data logging from the non-high speed logger?

Sean

[Matt Cramer]

The tooth logger plus the regular data log. (I generally prefer the tooth log to the composite log for Basic Trigger mode.)

[warlock.da.newbie]

Matt,

Thank you for the clarification. I will get a log out, hopefully tonight. Thanks for the additional information.

Also is there anything in particular I should start looking for? My configuration for this is based off of the article from DIYAutoTune.

https://www.diyautotune.com/support/tec ... tributors/


Sean

[warlock.da.newbie]

OK, attached are the main data log and tooth logger.

[Matt Cramer]

OK, it's getting a lot of noise pulses while cranking. Try adjusting the VR trim pots and / or increasing the Skip Pulses setting. Also, where is the MSD box grounded?

[warlock.da.newbie]

OK, it's getting a lot of noise pulses while cranking. Try adjusting the VR trim pots and / or increasing the Skip Pulses setting. Also, where is the MSD box grounded?

Matt,

Any chance you can add a screenshot and point out what is showing as noise? I'm completely lost right now on what the high speed logger should look like. In addition I am assuming I would look at moving R56 clockwise to adjust the trigger voltage on the VR circuit, correct?

As for my configuration I the MSD box is grounded to the chassis ground. The distributor's VR sensor ground is attached to pin 1 on the MS3, the shield is attached to pin 2 on the MS3.

Sean

[warlock.da.newbie]

All right, attached is the last data log of the night. This was with R52 turned two full turns clockwise from zero. I also attached a screenshot of what I am getting on the tooth logger. This does not look at all like examples posted on your website so I am assuming I am doing something wrong with my logging.

Thanks for the help and attention,
Sean

[Matt Cramer]

Here's some annotated pictures. With "Basic Trigger", the bar height is the time between pulses from the distributor, and they should all be about the same height. If the engine is accelerating, they get smaller; if it is slowing down, they get bigger. But this would be something like 10% bigger or smaller - you see something that's 90% smaller, that pulse shouldn't have happened.

[warlock.da.newbie]

Matt,

Thank you for the assistance. I finally sorted the issue out. The VR sensor in the distributor was outputting about 20mV during cranking. The noise that I was getting was overhead power lines that were inducing up to 5mV. I replaced the VR sensor in the distributor and verified that I was getting over 500mV during cranking. Second I confirmed with MSD that the CDI box had failed. After having the CDI box rebuilt the engine started up on the first try.
Time to finally start tuning.

Sean