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Electronic ignition conversion on 70 Dart #3040302
05/06/22 12:26 PM
05/06/22 12:26 PM
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warfordsburg, PA
dirt Offline OP
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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?

Re: Electronic ignition conversion on 70 Dart [Re: dirt] #3040318
05/06/22 12:50 PM
05/06/22 12:50 PM
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GomangoCuda Offline
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This Link shows the correct wiring. Please tell us where each of these wires goes on yours.


In theory, there is no difference between theory and practice. In practice, there is.
Re: Electronic ignition conversion on 70 Dart [Re: dirt] #3040331
05/06/22 01:20 PM
05/06/22 01:20 PM
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Anchorage, Alaska
metallicareload Offline
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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.


440, 4-Speed, 3.54
1968, when Dinosaurs ruled the Earth
Re: Electronic ignition conversion on 70 Dart [Re: metallicareload] #3040332
05/06/22 01:25 PM
05/06/22 01:25 PM
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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.

Re: Electronic ignition conversion on 70 Dart [Re: Sniper] #3040339
05/06/22 01:32 PM
05/06/22 01:32 PM
Joined: Oct 2005
Posts: 115
Anchorage, Alaska
metallicareload Offline
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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.


440, 4-Speed, 3.54
1968, when Dinosaurs ruled the Earth
Re: Electronic ignition conversion on 70 Dart [Re: Sniper] #3040340
05/06/22 01:33 PM
05/06/22 01:33 PM
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Posts: 1,342
warfordsburg, PA
dirt Offline OP
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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.

Re: Electronic ignition conversion on 70 Dart [Re: GomangoCuda] #3040343
05/06/22 01:37 PM
05/06/22 01:37 PM
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warfordsburg, PA
dirt Offline OP
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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.

Re: Electronic ignition conversion on 70 Dart [Re: metallicareload] #3040344
05/06/22 01:39 PM
05/06/22 01:39 PM
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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.

Re: Electronic ignition conversion on 70 Dart [Re: dirt] #3040345
05/06/22 01:44 PM
05/06/22 01:44 PM
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Anchorage, Alaska
metallicareload Offline
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It will IF the dark blue wire is energized when cranking, I don’t know if that’s the case or not


440, 4-Speed, 3.54
1968, when Dinosaurs ruled the Earth
Re: Electronic ignition conversion on 70 Dart [Re: Sniper] #3040350
05/06/22 02:00 PM
05/06/22 02:00 PM
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GomangoCuda Offline
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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.


In theory, there is no difference between theory and practice. In practice, there is.
Re: Electronic ignition conversion on 70 Dart [Re: dirt] #3040355
05/06/22 02:19 PM
05/06/22 02:19 PM
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Morristown Tn.
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71birdJ68 Offline
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What brand of conversion and when was the current one installed?

Re: Electronic ignition conversion on 70 Dart [Re: 71birdJ68] #3040358
05/06/22 02:32 PM
05/06/22 02:32 PM
Joined: Aug 2006
Posts: 1,342
warfordsburg, PA
dirt Offline OP
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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

Re: Electronic ignition conversion on 70 Dart [Re: dirt] #3040443
05/06/22 09:03 PM
05/06/22 09:03 PM
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Omaha Ne
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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

Re: Electronic ignition conversion on 70 Dart [Re: metallicareload] #3041383
05/11/22 07:01 AM
05/11/22 07:01 AM
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Berlin, N.J.
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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.


It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

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