Electrical problem?

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Jeff Seighman

aka jeffnmo
Joined
Jan 19, 2020
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Hey everyone, I have a 1970 340 Dart with a MP electronic distributor, MSD 6 box and a MSD blaster coil. I hooked up an MSD tach adapter and used the white wire for the tach trigger instead of the grey like I should have and ruined the Box, I disconnected the tach adapter and put in a new 6 box, the car starts fine and runs till I slow down then it shuts off, it starts back up and does the same. I checked the carb and its getting fuel. I checked the coil and it is with in specs. The car was running fine before the tach adapt fiasco. Thanks for any help.
Jeff
 
Do you still have that tach adapter attached?

When you say slow down than it shuts off, is it instantainous like turning off the key or like too slow of an idle.
 
Are you SURE you ruined the box? The tach box should be accepting an input driven by the MSD box. How did you determine this?

Anyhow I'd "unwire" the thing and hook it up "theft" style reduce it to the bare minimum wiring. Hook the big red and small red "jumper" direct to battery. Double check the big black is ground. Unhook ANYTHING else, tach, etc.

Also do you have ANYTHING connected to the coil except the two MSD wires? There should be no radio cap, no nothing, only the two MSD wires
 
I will try what you say. The MSD wires are the only wires to the coil. The light on the box didn't come on after I shut it off and nothing happened when I went to restart it after I found out I wired it wrong. It started instantly when I put in a new box, than this new problem popped up.
 
Have you read through the test destructions on the MSD site?
 
MSD was no help, going to move the small red wire to the battery today and see if I can figure this mess out.
 
The MSD box has 2 power wires. Constant 12V and switched 12V. I'm not sure why it would be shutting down at low RPM? I'm assuming you've got the constant 12V to the battery directly or to the starter relay? Where are you getting the 12V switched power from?
 
Did you set the rev limiter on the box? That’s if you have one. Just a suggestion.
 
Its not the MSD shutting down, I got under dash and wiggled the ignition switch wires at the connector and could the car shut off, it seems their is something wrong on the side of the connector to the dash harness. I'm going to remove some of the tape to see if I can see anything or isolate it to one wire. I closed up the female connectors a little so they should be making good contact. Thanks for the help.
 
No particular order........

Could be problem at the switch itself, at the column (switch) connector, or more likely the bulkhead connector.
 
I replaced the the switch a few months ago and cleaned and put dielectric grease on the bulk head connectors awhile back, I did wiggle all them wires and nothing happened, the only place the car shut off was at the ignition switch connector under the dash? and it seemed to be on the dash side of the harness. I think you are right its the switch connector. I'm not the best at electrical diagnostics so all the help is greatly appreciated. The worse part is I just rebuilt the engine a few months ago and it is running like a bat outa hell. No there is no other charging problems.
 
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