Ignition issues...

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Nick Mailloux

Nick Mailloux

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Hi guys! So my 73 dart has started running pretty crap tacular again. I believe the original 5 pin ignition module is going out. If you touch the transistor on it it shocks you which doesn't seem right. So I bought a new aftermarket 4 pin module and the car won't run with it. Took that one back and exchanged it and it still won't run. I did notice that when I turn the key off it will backfire. If I put the old one back on it will run but still crappy. Isn't the four pin supposed to work on a 5 pin harness?
 
Okay so I have power in the run position to the coil and at pins 1 And 3 on the module. But no spark... I even tried jumping the starter solenoid with it in run and no spark still.
 
A 4 pin should run on a 5 pin harness "the deal is" that with the 4 pin resistor, the "2nd half" of the resistor fed power (to the older) 5 pin ECU. The 4 pin does not need that

You MAY have a problem with ignition switch/ wiring/ bulkhead connector

Here is how a Mopar ignition switch works:

The "run" power which comes out in the engine bay feeds power (depending on year/ model) to the ignition system, alternator field, voltage regulator, sometimes some smog doo dads. THAT POWER IS ONLY HOT in "run." It GOES COLD IN "cranking." This power comes from the IGN1 terminal of the key/ ignition switch

So this means there must be a SECOND source of power for cranking and that comes from the IGN2 terminal of the switch. This is the "coil bypass" circuit and is the ONLY source of power for the ignition system during cranking

So clip your meter to coil + and see if you have power. If not you'll have to find out why. Next I'd access the ignition switch connector and see if you have it there

Go to MyMopar for free service manual downloads and other wiring diagrams. Some of them there, came from the guys here

NOTE: The ignition switch diagram in the 73 shop manual is drawn somewhat ambiguous. They imply that the yellow "start" terminal of the switch (which fires the start relay) and the brown bypass circuit are connected. THEY ARE NOT. They come off separate dedicated switch contacts.

There are many many posts on this issue on here, do a search
 
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Dist pickup reluctor etc., Coil, dist cap, rotor?????
 
Just solved it, the pickup was too far away, I set to .008 and it runs perfect now. It seams the older Mopar ignition boxs where a little less sensitive to the pickup relucter gap. The new ones have to be as close as possible or they don't work at all.
 
It absolutely could be week, although it's a new aftermarket distributor. It's probably just Chinese crap lol. Think I'm gonna order the Mopar licensed one from summit. It still triggered the factory unit but maybe the aftermarket parts store replacements are just sensitive. I measured the voltage the pickup generates, it's about .5 volts ac.
 
AJ/FormS said:
Hooray!
But you better get a spare pick-up; I never saw one (pre 2004), that wouldn't trigger the ECU at up to .030.. I gotta wonder if your pick-up isn't weak
Click to expand...

I've got a mixture of "unknown" 4 pin modules here, and at least 2, maybe 3 are a bit picky on gap.
 
About the transistor case shocking you, yes that is correct. It is a connection to coil (-). When the ignition triggers, the transistor turns off, the coil primary peaks to about 400V, the secondary winding multiplies it by about 80, so the peak spark voltage about 30kV.
Some say the new units have fake transistor case for show, use TO220 package transistor on inside.
About the pickup gap.The trigger is a change of reluctance. The pickup is biased with a magnet, the reluctor tooth pulls flux away, and as it passes the ignition triggers. The pickup voltage is proportional to rate of flux, the change of flux is related to gap, the rotation speed changes rate of change. Too much gap typically causes starting problems, before it causes running issues. There be other issues...
 
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"On that shock" years ago I had a Mopar ignition on a SB in an FJ-40 Landcruiser. The hood was not very "sealed." Before I figured it out, it would get water, snow, mud, dirt up under and onto the ignition box. It would miss badly sometimes, before I finally figured it. Moved the box through the firewall with the coil under there too LOL
 
67Dart273 said:
"On that shock" years ago I had a Mopar ignition on a SB in an FJ-40 Landcruiser. The hood was not very "sealed." Before I figured it out, it would get water, snow, mud, dirt up under and onto the ignition box. It would miss badly sometimes, before I finally figured it. Moved the box through the firewall with the coil under there too LOL
Click to expand...
That's what mine was doing without the moisture or water getting to it. Mine seemed to be heat mostly. It would start and run great on cooler days but after it warmed up it would miss and run like crap. On warm days it would just run like crap no matter what. I've driven it about 100 miles now in 90 degree weather without issue after changing the module and adjusting the pickup.
 
It is always possible that dirt/ corrosion has gotten under the transistor/ heat sink and formed a conductive goo. "The shock" if you read earlier is completely normal. The neg side of the coil can spike to hundreds of volts.
 
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