Carmine
Old Man with a Hat
I just purchased a Lean Burn-era C-body that had been converted to standard electronic ignition using the Mopar Performance kit. The owner told me the car had been running, but when he went to move it for me to look at, it refused to start.
Upon my arrival, I noted a none-to-clean installation. A rat’s nest of wires, random color codes, a second ballast mounted next to another, etc. I figured the problem lay herein. BTW, this is why I (and others) are so down on altering originality to "solve" a problem. Most people end up adding to them!
While there I pulled the coil wire and Mrs. Carmine cranked the engine. Sure enough, only a spark when shutting down. This happens because removing power from the coil induces the HV charge. That on/off cycling is what points do mechanically, or in the case of an electronic system, a difference in magnetic field is detected by the pick-up coil. (There are eight sharp points that rotate past the pick-up without contact, each correlating to a cylinder.) However, this signal is not strong enough to be used to turn the coil on/off, as with mechanical points, so it’s amplified by a switching transistor. (The exposed thick-nickel-sized thing on the ignition module). The switching must occur very quickly… At 5000 RPM it would be 40,000 times in a minute (5000 x 8). At those speeds, (or after 30k miles) the electronic switching, lack of electrical arcing and no contacting parts become advantageous.
A deal was struck that included towing the car back to my house (roughly 60 miles). I let the tow driver plop it on the driveway like a sick rhinoceros, figuring I’d have the problem fixed in 30 minutes at most.
The first thing that caught my attention was the black/yellow wire from the ignition module running to ignition coil POSITIVE. This is supposed to be the on/off signal, not the power supply. It should be connected to coil NEGATIVE. A coil will work when wired backwards, but at reduced efficiency. It’s sort of like tuning on your toaster on by unplugging it instead of pressing the lever. So I corrected this, but not surprisingly, it didn’t fix the issue.
This is where @rags suggestion to plug a known-good distributor into the harness was helpful (as well as owning another 70s Mopar). To verify the known-good aspect, I plugged my spare into my ’76 Royal Monaco’s system and low and behold, plenty of sparks from the coil wire to ground as I spun the distributor with the key “on”. I repeated this on the sick rhinoceros and NO SPARKS.
So what gives? I had power everywhere I should; at the coil, across the ballast, to the module and a good solid ground between firewall and the module. I knew the coil could at least produce ONE spark when shutting down. I’d checked the two wires running to the installed distributor and there were no continuity issues. On a hunch, I wiggled the module connector while spinning the spare distributor. SPARKS!
So I took a closer look at said connector. It didn’t have the screw running through it, as would any actual Chrysler module connector. Not only that, the China-knockoff module had no way of even threading a screw in!
So I swapped in a used, 40+ year old box with a screw and even I was surprised how much further this moved the connector onto the module. Now the spark was consistent when using the test-distributor.
Oh boy, I’m getting so excited to start the car! And one cough, then dead again. Maybe those plugs are fouled from all the attempted starts? So I pull a few of the easy ones, but they look pretty good.
That must mean that in addition to the bad wiring and crappy-design module, the pick-up coil must be bad as well. A three-problem stack-up, but still an easy fix. So I pull the cap to start removing the distributor and I notice this:
Obviously the rotor isn’t supposed to randomly spin. Hopefully the issue isn’t a broken oil pump/distributor intermediate shaft. It wasn’t, it was this:
Poorly made re-pop distributor shaft was relying on a press-fit to keep everything together. I gave up on the troubleshooting and decided to cut a car in half to relieve stress.
The shaft would have to wait until Monday’s lunch for me to avail myself of a genuine Chrysler-sourced TIG weld.
I did that and installed the distributor back in the car. Of course the timing is completely gone, so I had to start from scratch with the damper lined up at 0-degrees, which could either be the compression stroke (squeeze) or exhaust (blow) and I’m not pulling the valve cover just to figure it out. I gave it a spin and got some slow cranks and coughs. Moved the timing around a bit which yielded more of the same. Lifted the distributor and spun 180-degrees, this yielded nothing. Then “life” got in the way and I had to quit for the day. Hopefully I’ll have some more time to spend on it tonight.
Upon my arrival, I noted a none-to-clean installation. A rat’s nest of wires, random color codes, a second ballast mounted next to another, etc. I figured the problem lay herein. BTW, this is why I (and others) are so down on altering originality to "solve" a problem. Most people end up adding to them!
While there I pulled the coil wire and Mrs. Carmine cranked the engine. Sure enough, only a spark when shutting down. This happens because removing power from the coil induces the HV charge. That on/off cycling is what points do mechanically, or in the case of an electronic system, a difference in magnetic field is detected by the pick-up coil. (There are eight sharp points that rotate past the pick-up without contact, each correlating to a cylinder.) However, this signal is not strong enough to be used to turn the coil on/off, as with mechanical points, so it’s amplified by a switching transistor. (The exposed thick-nickel-sized thing on the ignition module). The switching must occur very quickly… At 5000 RPM it would be 40,000 times in a minute (5000 x 8). At those speeds, (or after 30k miles) the electronic switching, lack of electrical arcing and no contacting parts become advantageous.
A deal was struck that included towing the car back to my house (roughly 60 miles). I let the tow driver plop it on the driveway like a sick rhinoceros, figuring I’d have the problem fixed in 30 minutes at most.
The first thing that caught my attention was the black/yellow wire from the ignition module running to ignition coil POSITIVE. This is supposed to be the on/off signal, not the power supply. It should be connected to coil NEGATIVE. A coil will work when wired backwards, but at reduced efficiency. It’s sort of like tuning on your toaster on by unplugging it instead of pressing the lever. So I corrected this, but not surprisingly, it didn’t fix the issue.
This is where @rags suggestion to plug a known-good distributor into the harness was helpful (as well as owning another 70s Mopar). To verify the known-good aspect, I plugged my spare into my ’76 Royal Monaco’s system and low and behold, plenty of sparks from the coil wire to ground as I spun the distributor with the key “on”. I repeated this on the sick rhinoceros and NO SPARKS.
So what gives? I had power everywhere I should; at the coil, across the ballast, to the module and a good solid ground between firewall and the module. I knew the coil could at least produce ONE spark when shutting down. I’d checked the two wires running to the installed distributor and there were no continuity issues. On a hunch, I wiggled the module connector while spinning the spare distributor. SPARKS!
So I took a closer look at said connector. It didn’t have the screw running through it, as would any actual Chrysler module connector. Not only that, the China-knockoff module had no way of even threading a screw in!
So I swapped in a used, 40+ year old box with a screw and even I was surprised how much further this moved the connector onto the module. Now the spark was consistent when using the test-distributor.
Oh boy, I’m getting so excited to start the car! And one cough, then dead again. Maybe those plugs are fouled from all the attempted starts? So I pull a few of the easy ones, but they look pretty good.
That must mean that in addition to the bad wiring and crappy-design module, the pick-up coil must be bad as well. A three-problem stack-up, but still an easy fix. So I pull the cap to start removing the distributor and I notice this:
Obviously the rotor isn’t supposed to randomly spin. Hopefully the issue isn’t a broken oil pump/distributor intermediate shaft. It wasn’t, it was this:
Poorly made re-pop distributor shaft was relying on a press-fit to keep everything together. I gave up on the troubleshooting and decided to cut a car in half to relieve stress.
The shaft would have to wait until Monday’s lunch for me to avail myself of a genuine Chrysler-sourced TIG weld.
I did that and installed the distributor back in the car. Of course the timing is completely gone, so I had to start from scratch with the damper lined up at 0-degrees, which could either be the compression stroke (squeeze) or exhaust (blow) and I’m not pulling the valve cover just to figure it out. I gave it a spin and got some slow cranks and coughs. Moved the timing around a bit which yielded more of the same. Lifted the distributor and spun 180-degrees, this yielded nothing. Then “life” got in the way and I had to quit for the day. Hopefully I’ll have some more time to spend on it tonight.
