73 electronic ignition help

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Jake leathers

Jake leathers

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My 73 Plymouth duster was running great, shut it off to talk to a guy and would not start back up. No spark. It's been a few months now, I got a new ECM, ballast resistor, coil, and a new harness to tie everything together. I even tried putting on another distributor I had laying around, still nothing. I noticed that the ballast resistor gets kinda hot I don't know if that's normal or not. Anybody have any ideas? Thanks
 
the ballast resistor does dissipate heat. try running a wire from the positive side of the battery to the positive side of coil
 
I have tried that. And I have voltage going to coil in run position and higher voltage when cranking.
 
Pull the cap and see if the rotor is turning while you crank it. Happened to a friends 318 years ago - chain fell off as it shut off. It's a long shot, though.
 
What engine? If its a slant six pull the distributor and check the drive gear.
 
First thing to do is either measure coil + voltage or jumper battery power to the coil +

If you do the last, don't leave it hooked up any longer than needed to troubleshoot.

With key in "run" you should have 8V or more at the coil+

With key "cranking" in start you should have "same as battery" at coil+

Next, turn key to "run". Disconnect the distributor pickup connector, take up the firewall end of the connector and repeatedly tap the bare terminal to ground. This should generate one "snap" spark each time

Remove the cap, inspect inside the dist. Look for rust, play, strike damage, and debri in and around the pickup coil/ reluctor

"Work" the distributor connector in / out several times to scrub the terminals and "feel" for tightness. These can be troublesome
 
I touched the distributor connector to ground and the distributor did spark. I cleaned up all contacts in cap and on rotor, and my voltage is good going to coil, but I still have no spark.
 
OK did you check if you have voltage to the coil WHEN CRANKING. There are two different sources involved.
1...."Ignition run" usually blue, IGN1 from the key. This is hot ONLY in "run" and NOT "start."

2...."Coil bypass" usually bronw, IGN2 from the key. This is hot ONLY in start. It provides coil starting voltage, and bypasses the resistor

If you HAVE voltage "when cranking" and no start, the problem is most likely........

(no particular order...........)

Too much gap at reluctor / pickup adjustment
Damage to reluctor/ pickup or excessive play in shaft, bushings
Poor connection at distributor electrical connector
Bad pickup coil
 
MoparLeo said:
bypass the ballast resistor and try to start.
Click to expand...

You should be able to UNPLUG the ballast and it should fire and run "on the starter." This was my point above. The "bypass" starting circuit from the ign switch bypasses the ballast
 
67Dart273 said:
You should be able to UNPLUG the ballast and it should fire and run "on the starter." This was my point above. The "bypass" starting circuit from the ign switch bypasses the ballast
Click to expand...
Shoot me if I'm wrong but I don't think it bypasses both circuits of the dual resistor. Both circuits are in a single connector ( blue is jumped to both ) so unplugged might not start.
 
what is the actual voltage at the coil+ in run?
what is the actual voltage at the coil+ while cranking?
 
I just check the voltage and it is only 5 volts on run and 8 volts when cranking. What could be causing that?
 
what is the actual voltage going into the ballast?
 
I’d say you have a wiring issue, either under the dash or at the bulkhead connector..
 
Jake leathers said:
I just check the voltage and it is only 5 volts on run and 8 volts when cranking. What could be causing that?
Click to expand...


5V in run with engine stopped? That "could" be normal. The 8V cranking is not. FIRST thing to do is get a factory shop manual, access the connector for the ignition switch and see what the voltage is at the same electrical point at that connector. That will give you some idea if you have a drop through the bulkhead connector. Could be the switch itself........check voltage going TO the ignition switch

You can download the factory manual free from MyMopar, and by the way, that manual came from a few of the guys right here
 
Alright thanks everyone for the fast responses. Thanks 67Dart I will use Mymopar. I will just chase everything down. It might be a couple of days before I get back on here. I will post what I find out.
 
Keep in mind people talk about "wiring" but in reality the trouble is almost always connectors, terminals, and switches, and sometimes fuses and fuse clips. There are no fuses in this part of the circuit

ANOTHER POINT that comes to mind, Redfish on here has pointed this out..........the late model cars have an engine harness connector, look for a WHITE colored connector.......they often give trouble. Best advice is to cut it out and splice the wiring direct
 
Yes I do have that engine wires connection. That was one of the first things I tried was bypassing those wires going through there that go to the coil. I think I might just get rid of that thing all together like you said.
 
Next places I would look for is bad connections in the bulkhead connector, the ignition switch connector, and the switch itself. A voltmeter is the best friend you have right now
 
They will run on low voltage. In fact they do. The ballast resistor lowers the voltage to the coil and the 5 pin ecu. They won't start on low voltage though. That's why they have a separate start circuit. Anyway... The fusible link and bulkhead is a good place to start looking for your voltage drop. If all good there, check the ignition switch connector under the column.
If you had about 12 feet of good wire you could temporary a route around, run it from battery positive to that ign' switch connector ( largest black wire there ). If it fires right up the fault is somewhere between the engine bay side and that connector which includes the ALT' gauge. We saw picks of one of those gauges melted down a just few days ago, and it was in a 73 model dash.
This fault would lower voltage to everything except the starter. Headlights, etc.., would work just not as good as they should. So maybe the first check would be, What else is operating on less than 12 volts? If everything except ignition is getting good current, the ignition switch and the blue with white tracer through the bulkhead is suspect. They added a choke heater to all the stuff already pulling through this wire. We've seen this wire connection melted recently also.
By the way, the ballast resistor shouldn't get kinda hot. It should get very hot. That's why its ceramic encased.
 
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