Electrical driving me nuts

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My383duster

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Hello everyone, I have a issue with my old 1973 Plymouth duster. Has a 383/727 for 25 years now. (It has electronic ignition )not wanting to start at times.It will not fire (some times) after the first start of the day..It starts right up every morning and if I shut it off and try to re-start it's not getting fire. I have replaced the ballast, Checked the coil, checked all of the wiring and connection's, Replaced the pick up coil in the distributor,Cleaned the ground where the control box is bolted,Replaced the control box etc.. I was messing with it yesterday and noticed that when it does this, When I'm turning it over and let off the key switch it will try to fire and start up. It seams like I have ran into this before on a Dart I was working on, But I can't figure this out.It runs great and does not try to die on me when driving it. WHAT AM I MISSING??. I know I'm getting old and forgetful but I just can't figure it out. I think I need some of that new medicine for memory . Any help or suggestions will be greatly appreciated. Thank you.
 
Last edited:
Year and model...
Offhand, in general, when it acts up, see if the coil is getting power in the start position. If not, start tracing it back from there and see where the feed is interrupted. Pay special attention to the bulkhead connections.
It's the IGN 2 feed from your switch on the wiring diagram in your Factory Service Manual.
You Do have a FSM, don't you?
Go to mymopar.com for a free download.
 
Professor Fate said:
Year and model...
Offhand, in general, when it acts up, see if the coil is getting power in the start position. If not, start tracing it back from there and see where the feed is interrupted. Pay special attention to the bulkhead connections.
It's the IGN 2 feed from your switch on the wiring diagram in your Factory Service Manual.
You Do have a FSM, don't you?
Go to mymopar.com for a free download.
Click to expand...
Thank you,I will check it today.
 
Realize how the key/ start circuit/ sequence works

You have TWO circuits for start and run on all these girls

In "run" the ign1 circuit FROM THE KEY goes out through the bulkhead connector (NOT fused, by the way), and depending on year model, feeds power to the ignition system (ballast and ECU box), branches off to feed the VR, alternator field on 70/ later, idle solenoid, electric choke if used, and a couple of smog doo dads up later on

THIS RUN POWER GOES DEAD WHEN cranking.

The ONLY power to the ignition system is from the IGN2 contact in the ignition switch which is live ONLY IN "start." This (usually) brown wire goes out the bulkhead, to the coil + side of the ballast.

THIS WIRE then is the only power to the ignition for cranking

On an electronic ignition , this is a "trick" circuit. This wire goes to the coil side of the ballast and feeds the coil full battery power for start. HOW DOES the ECU get power? This IGN2 power feeds BACKWARDS through the ballast, and from there backfeeds along the what is normally the IGN1 line to the ECU box. This means that during starting, the ECU is ACTUALLY only getting perhaps 5-6V to start. This in fact is normal and how it works

How to troubleshoot?

Check voltages. Clip a multimeter to the coil + terminal and ground, turn the key to "run". You should see NOT full 12V, but somewhere between 4-10V "or so" This is because the coil is drawing current through the resistor and dropping the voltage down

Now check the "start/ crank" condition. With your meter still in place, watch the meter while twisting the key to "start." Now you should see "same as battery." In other words, if the starter drags the battery down to 11.5 during cranking, then that is about what you should read at the coil. You rarely do because of circuit drop. But you SHOULD see AT LEAST 10.5V or more during this test.

Since you are having problems, I'd check these 3-4 times because IE if the key switch contact is flakey, it might show "good" one time and "not" the other

IF THIS voltage does not show good, I'd check the bulkhead/ firewall connector for that circuit, the key switch connector, and the switch itself
 
Thank you very much for the great information. I now remember the 1-2 start/run circuit after reading this information.I am sorry for not listing the year. 1973 Plymouth Duster . Was a slant 6 car when I bought it 26 year's ago. I built a 383/727 and put it in 25 years ago. Thank you again.I am gonna go run this test and re-run all of the wiring again right now.
 
Problem Solved.Thank y'all for the help!!. Brown wire from bulkhead going through the harness was broke at a connection.
 
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