MSD won't trigger off Mopar electronic distributor!!!!

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dgc333

dgc333

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I picked up an MSD 6A and went to install it today and it wouldn't start. Followed MSD'd trouble shooting guide and the MSD is producing a spark when either the white wire is grounded or the purple & green wires are jumped.

This tells me that the green / purple wiring is not getting a signal from the magnetic pick-up in the distributor. Double and Triple checked my wiring and connections with no luck. I can re-hook up the ECU and the engine runs fine.

What I did do was leave the MSD hooked up like it was a points ignition and used the (-) coil wire from the ECU to trigger the white wire on the MSD. Runs great.

My questions is shouldn't I be able to eliminate the ECU and trigger the MSD right directly from the distributor?

Any insites are welcom.
 
You did try the msd with the ecu unhooked and the plug at the distrubtor unplugged as well right? and the msd trigger (small red) wire has power in the crank and run position too...
 
The MSD has two ways of triggering.

When you have an electronic distributor with a magnetic pick-up you use the green & purple wires to trigger the MSD. I had these connected to the two wires coming out of the distributor and the ecu was not in the car. This would not work.

The other way is by grounding the white wire as would happen if you were using points to trigger the MSD. Since the mopar ECU is just an electronic switch I re-installed it and hooked the wire from the ECU to the negative of the coil to the white wire of the MSD and plugged the ecu into the distributor, the MSD is still attached to the coil. This works fine.

The small red wire is a low current power lead that turns the MSD on and off with the key. I have no issue here since the MSD unit works. I have seen many MSD installations where the ecu is not used so I am assuming the MSD is being triggered off the distributor pick-up. I trying to figure out what I am missing. I have sent a note to MSD's tech line put they won't respond until at least Monday.
 
did you say that you put the white wire to the neg side of coil? is the orange on the + side and the black on the - side of coil? did you run green to the black wire on the elec. dist. and violet to the orange/grey wire? is your red hooked to 12v source not the reduced voltage side of ballast?
 
No, The orange wire and small black from the MSD are on the + and - on the coil. The small red is on a switched 12v source, there is no ballast used with an MSD. The large red is attached to the primary 12v feed from the battery on the starter relay, large black is on the block.

The violet and green hook up to the pick-up wires coming out of the distributor. It is this configuration the car won't run. From other forums the concensus is either the pick-up in the distributor is not putting out enough signal to trigger the MSD or the MSD has a problem in this circuit.

The way I am running it is to hook the distributor up to the mopar ecu like it would be without the MSD and the black with yellow tracer from the ecu that would normally would hook to the - side of the coil is hooked to the MSD white wire. The MSD is still hooked up as it should be otherwise.

I am going to wait to see what the MSD tech folks have to say before I change anything since it's running extremely well now. Ultimately I would like to get the ECU out of the circuit.
 
I have mine hooked up to the pickup in the distributor as you are trying and it works great. I have eliminated the balast resistor, the mopar ecu and the associated harness that came with my electronic conversion kit. The green and purple wires are connected directly to the factory plug on the distributor.

Are you sure your white wire isn't grounding out when you have it disconnected for using the magnetic pickup? I made sure mine was secured out of the way and insulated properly.

Everything works great.
 
I had the white wire taped off and I am sure it was not shorting to ground. I have heard from another person that the pick-up in the distributor can be fussy requiring a smaller gap than the 0.008". I will try that and another pick-up.
 
try running the heavy black lead to the battery. also, is the switched 12v source actually getting 12 volts? did you do their test on that connector? put a jumper wire from the violet to green and turn the key on. when you pull a wire out it should spark.

http://www.msdignition.com/1troub1.htm
 
The heavy black wire is grounded to the block. I checked and there is <0.1 ohms of resistance between the attachment point on the block and the battery terminal which effectively is the same potential. In any case the MSD works so it's not a ground issue.

Yes the switched 12 volt is 12 volts but again this is just to turn the MSD on an off. The power to make it work comes via the heavy red and black wires and MSD's spec states the unit will work with a supply voltage of 10-18 volts.

I did get a chance to talk to MSD yesterday and it certainy seems like the pick-up in the distributor is the issue even though it will trigger the stock ecu. The MSD tech support person was very quite confident that if I can get a spark by shorting the green and purple wires that that circuit is working properly. In anycase it's a cheap an simple fix to install a new pick-up so I will be giving that a try.

In the mean time the MSD is working fine while being triggered by the ecu so I am getting the benifits.

I thank all for the inputs and will let the group know how I get it resolved.
 
Well I figured out why my MSD would not trigger off the distributor and I feel foolish that I didn't check that in the beginning.

I purchased a two pin trailer connector at the parts store so I could splice it onto to the MSD harness so I wouldn't have to disturb the wiring on the distributor. Well the trailer connector did not fully seat into the connector on the distributor and wasn't making contact.

Once I replaced the connector with the end I had from an old distributor it fired right up.
 
at least your diagnosis led you to know alot more about MSD and ignition systems in general. knowledge is a great thing.
 
now that all is making contact correctly - are you going to diconnect the ECU from the circuit. I believe that is the way the MSd was designed to be used. I kept the ECU, resistor and wiring harness as a backup and added a double spade with connectors on the coil. Then if the MSD should fail (and some do), you have a ready backup under the hood via switching a couple of wires.

Happy Trails :thumbup:
 
The mopar ecu is in the trunk (the ballast is still on the firewall but nothing is attached to it) and the MSD is now being triggered directly off the distributor. All the wiring to put the mopar ecu back is there and can be accomplished in about 10 minutes. I contemplated leaving it mounted but figured it is safer and less likely to have a latent failure if it's in my spares kit in the trunk.
 
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