Moparts

Electronic ignition conversion on 70 Dart

Posted By: dirt

Electronic ignition conversion on 70 Dart - 05/06/22 04:26 PM

My 1970 Dart had an electronic ignition conversion done in 1992 using the single ballast resistor not the double. I have been having problems with it just shutting off or not wanting to start recently. I had no spark. I was checking voltage at different locations and going by wire diagrams to see if the wiring was OK. I found the bad connection. But in the process I realized that the wire run wire and the start wire to the pin on the ecu were backwards. It is drawing power through the resistor when it is running and it draws power direct in the start position. According to all the diagrams I can find that is wrong. So my ballast resistor is powering both the coil and the ecu in the run position. In 30 years I have only had to replace the resistor and ecu 1 time. Only driving about 1000 miles a year.
I am thinking I should rewire this thing the right way unless I am missing something? Does that sound right?
Posted By: GomangoCuda

Re: Electronic ignition conversion on 70 Dart - 05/06/22 04:50 PM

This Link shows the correct wiring. Please tell us where each of these wires goes on yours.
Posted By: metallicareload

Re: Electronic ignition conversion on 70 Dart - 05/06/22 05:20 PM

iagree
You want 12+ volts at all times powering the ECU. That might explain some of the no starts, voltage drop when cranking and coming through the ballast resistor might be so low the ECU doesn’t know it should be firing.
Posted By: Sniper

Re: Electronic ignition conversion on 70 Dart - 05/06/22 05:25 PM

Originally Posted by metallicareload
iagree
You want 12+ volts at all times powering the ECU. That might explain some of the no starts, voltage drop when cranking and coming through the ballast resistor might be so low the ECU doesn’t know it should be firing.


Full battery voltage in start ONLY. Thru the ballast in run. Go look at the wiring diagram Gomango linked.
Posted By: metallicareload

Re: Electronic ignition conversion on 70 Dart - 05/06/22 05:32 PM

Originally Posted by Sniper
Originally Posted by metallicareload
iagree
You want 12+ volts at all times powering the ECU. That might explain some of the no starts, voltage drop when cranking and coming through the ballast resistor might be so low the ECU doesn’t know it should be firing.


Full battery voltage in start ONLY. Thru the ballast in run. Go look at the wiring diagram Gomango linked.


Full battery to ECU cranking and running.

Full battery to coil when cranking.

Thru ballast to coil when running.
Posted By: dirt

Re: Electronic ignition conversion on 70 Dart - 05/06/22 05:33 PM

If you look at the diagram it does not show full voltage to ecu in start position only. The ecu should get full voltage in the run position. According to that diagram. But not in start position.
Posted By: dirt

Re: Electronic ignition conversion on 70 Dart - 05/06/22 05:37 PM

My ecu is wired backwards from what that diagram shows. It is getting full power in start position and power through the ballast resistor in run position.
Posted By: Sniper

Re: Electronic ignition conversion on 70 Dart - 05/06/22 05:39 PM

Originally Posted by metallicareload
Originally Posted by Sniper
Originally Posted by metallicareload
iagree
You want 12+ volts at all times powering the ECU. That might explain some of the no starts, voltage drop when cranking and coming through the ballast resistor might be so low the ECU doesn’t know it should be firing.


Full battery voltage in start ONLY. Thru the ballast in run. Go look at the wiring diagram Gomango linked.


Full battery to ECU cranking and running.

Full battery to coil when cranking.

Thru ballast to coil when running.


You know what, you are right.
Posted By: metallicareload

Re: Electronic ignition conversion on 70 Dart - 05/06/22 05:44 PM

It will IF the dark blue wire is energized when cranking, I don’t know if that’s the case or not
Posted By: GomangoCuda

Re: Electronic ignition conversion on 70 Dart - 05/06/22 06:00 PM

Originally Posted by Sniper
Originally Posted by metallicareload
iagree
You want 12+ volts at all times powering the ECU. That might explain some of the no starts, voltage drop when cranking and coming through the ballast resistor might be so low the ECU doesn’t know it should be firing.


Full battery voltage in start ONLY. Thru the ballast in run. Go look at the wiring diagram Gomango linked.

Might want to look at the link again. The coil is the one that gets 12V at start only and goes through the resistor at run. Full voltage to the ecu. Does not go through the resistor.
Posted By: 71birdJ68

Re: Electronic ignition conversion on 70 Dart - 05/06/22 06:19 PM

What brand of conversion and when was the current one installed?
Posted By: dirt

Re: Electronic ignition conversion on 70 Dart - 05/06/22 06:32 PM

It was a Mopar performance conversion kit that was done in 1992. It is still the same wiring today. I could have screwed it up back then. I was only a teenager working on my first car. Lol
Posted By: TJP

Re: Electronic ignition conversion on 70 Dart - 05/07/22 01:03 AM

Had a customer several years back with a random no start problem. He wound up here on a recommendation after several shops couldn't fix it but took his money claiming they had whistling
I asked him what do you do when this occurs? he said wait. i asked how long? Usually 20 minutes to an hour.
I found the exact thing you are describing. The ECU power was going through the ballast. OOPPS!
I corrected the wiring. When he picked it up he said "I'm not convinced you fixed it as I have been told this many times" I said bring it back if it happens again. So every time I saw him at a show I'd ask if it had failed yet. he always said no. After a few years he would just say NO without my saying anything LOL. I'll have to ask him again next time I see him as it's been about 20 years now laugh2
I'll close with saying electronic devices are not always predictable. Sometimes a 12V device will function on 8-9 V and sometimes it won't depending on a ton of variables, mainly it's mood LOL twocents
Posted By: abodyjoe

Re: Electronic ignition conversion on 70 Dart - 05/11/22 11:01 AM

Originally Posted by metallicareload
Originally Posted by Sniper
Originally Posted by metallicareload
iagree
You want 12+ volts at all times powering the ECU. That might explain some of the no starts, voltage drop when cranking and coming through the ballast resistor might be so low the ECU doesn’t know it should be firing.


Full battery voltage in start ONLY. Thru the ballast in run. Go look at the wiring diagram Gomango linked.


Full battery to ECU cranking and running.

Full battery to coil when cranking.

Thru ballast to coil when running.



this is the correct way.
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