Ignition problems - resolved

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Ignition problems - resolved

Post by keithg on Tue Apr 26, 2016 9:30 am

I posted this on the yahoo group, but thought I'd post a summary here for others to learn from (and for when Yahoo Groups goes away) and so I do not forget.

Car was always hard to start hot. Car recently started dying about 10 minutes after starting. Wait a few and start back up. No amount of cranking would work. Had to wait. It has a pertronix ign in it. Carb was all ok, clean and worked fine (Carter 400). Put a MSD Blaster 2 coil I had around in it and it was hard to start, but when running it was better than ever. Just hard to start. Checked voltage at the coil with the ign on and it was ~5v. The car had only the one yellow wire at the coil (manual calls for 2 wires - more later). This low voltage was a symptom of age, wire being splice repaired and potentially corrosion on the splices or something. There should be ~9v at the coil with the ign 'on', a fully charged battery. This yellow wire goes to the ign switch and is a 'Resistance Wire' on the wiring-diagram. It should be about 0.3 ohms (based on my calculations) or so from the switch to the coil. Mine was closer to an ohm (the most accurate way to check this is by voltage drop and using V=I*R as most meters are not accurate at these low resistances).
In addition to this the black wire from the switch to the coil was missing. The black wire gives battery voltage to the coil only when cranking so that there is a bit more voltage to get decent spark energy while the starter is pulling the voltage down. It is energized only in the 'start' position and is switched out in 'run'. After reading the Pertronix 1181 Instructions they suggest 12Ga for the 8A coil current. They also do not specifically suggest the bypass wire (Black in the diagram). I had 14Ga, so am going with that. It is larger than the OEM and I'm running it a shorter length down the driver side fender, anyway. I used an MSD Blaster 2 coil as I had it 'on hand' from a previous project. To use it and most other Stock replacement and performance coils (the exception is the pertronix flamethrower coil which is 'internally ballasted') you need the ballast resistor, so I got a Chrysler Ballast Resistor from AutoZone for $5.00 and wired it inline to replace the yellow 'resistance wire'. I bolted it to the underside of the diagonal brace next to the master cylinder.  I now get ~9V at the coil at idle and it starts and pulls so much better.

Hope this helps someone,

Keith (In Portage Park, Chicago)


Last edited by keithg on Tue Apr 26, 2016 10:39 am; edited 1 time in total

keithg

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