Mopar distributor and MSD box

[flatbill]

I am using an electronic, no advance Mopar distributor and an MSD 6A box. I have set up my system parameters as described in the MSD box writeup. That is,

ignition input capture rising edge
cranking trigger trigger rise
coil charge scheme standard coil charge
spark output going low, normal
max spark dwell 25.5

I am not using the HEI module between the distributor and the relay box

I came across another Mopar description and found some differences the the parameters. Now I wonder if this might be the cause of some of my difficulties.

The Mopar description calls out for the following parameters,

trigger offset 10 degrees
ignition input capture falling edge
cranking trigger trigger rising
coil charge scheme standard coil charge
spark output going high normal

Lately, and at times in the past, I have had problems with noise on the vbat ( I have some suggestions that I have not tried yet ) , unpredictable running, etc. The last time I started it, it failed to start the first time, just chugger a couple times then quit. The second time it popped back through the intake. Then it started, rough at first then smoothed out.

I was digging looking for more information and came across this difference in the two setups. Do I need the HEI module, then set it up that way? Or do I set it up without and use the parameters listed for that?

I plan to review all the wiring on the system and the grounding.

Thanks for any help. Billk

MSII V3 set up for VR, fuel and spark, GM throttle body, locked Mopar distributor

[Matt Cramer]

You don't need a HEI module with a V3.0 or later board.

Does the timing you see with a timing light match the timing you see in the tuning software through the entire rev range? If it does, I wouldn't worry about the settings.

[flatbill]

I finally got back on the MS. I replaced the msd box with a digital clone of an msd 6A box from Summit. The car started right up and seemed to be much better, but not quite there yet. I redid the wiring as follows,

Ran ignition box power and ground wires right to the battery, routing away from the distributor and coil wires
Added a 27000 mfd capacitor to the power leads close to where they enter the box
Made a twisted pair for the msd trigger wires to the box

Seemed to start up OK and run well

Had a friend set up his O'scope on the ecm and adjust the 2 pots.

As he adjusted the pots the rpm idle rpm could be made to go up and down. The advance seemed to change aslo as shown on the dashboard display.

Could get the motor to die if you adjuste wrong.

Didn't seem to get the same scope patterns as shown in the DIY write up.

I am going to try to attach a screen shot of the O'scope display. Its a BMP file. I hope you can see it.

Also a datalog after we adjusted the pots to give the as shown display.

When making the run and the data log, there was not a smoothness that I would have wanted. I think I have more tuning to do now that the pots have been adjusted.

Can you give me an opinion on the O'scope display? Any suggestions based on what you see would be appreciated.

MSII V3 board, GM throttle body, Mopar locked electronic distributor VR sensor. MSD type ignition box.

Thanks, Billk

[flatbill]

Is there something causing the noise on the mapdot line? It seems that I saw something about putting a filter in the vacuum line to smooth out the signal. Would this be a good idea? What would be a good suggestion on a filter? Seems like I read about a fish air line filter. Thanks, Billk

[Matt Cramer]

From that oscilloscope trace, looks good, just be sure Ignition Input Capture is set to Falling Edge.

While the MAP trace could be steadier, I don't see it causing you any particular problems in that log, either.

[flatbill]

I just checked and the input capture was set to rising edge as per the info I got on setting up for the MSD box. I reset it to falling edge and it started and ran well. I didn't get to get it all warmed up and drive it. I will do this. I think I will also have to recheck the timing to see if this changes it.

This makes a lot of sense after looking at the O'scope screenshot. Seeing the 2 curves cross on the downward leg has to be the signal on the falling edge. The mopar distributor info says to use fallling edge, but the msd says rising. I just chose the wrong setup.

Matt, Thanks again for some really great analysis of my problem. Billk

[flatbill]

I think I should get a prize for doing everything wrong the first time and usually wrong the second time too.

After saving the changes from rising edge to falling edge I shut the motor down and thought I had done the right thing. When I went to restart the motor, it ran really bad. It dawned on me that the change from rising edge to falling edge should make a large difference in the ignition timing. The change didn't take effect until I restarted MSII with the motor restart.

I pulled out my timing light and found the timing very retarded. I (foolishly) loosened the distributor and adjusted the timing on the balancer to match what was showing on the TS dashboard. The motor ran better again.

Went for a test drive. The motor would miss when accelerating briskly. I then rethought the timing process and thought about rotor phasing.

I rotated the motor to 10 degrees BTDC on the balancer. I pulled the distributor cap and saw that the rotor was way off on alignment with the #1 plug wire contact. There was a scorched spot in the cap near at least one of the cap contacts. I rotated the distributor to align the rotor with the cap contact at the 10 degree advance location. I started the motor and used the trigger wizard to get the balancer reading to match the trigger wizard number. What a difference.

I think that if it were not for the strong spark of the MSD box the motor might not have even run. Sorry to be so slow on the thought processes and I appreciate your patience with helping me. Also, if there are flaws in the way that I did this, please let me know. Thanks again, Billk