I recently posted on rec.autos.tech about the problems I was having with an MSD 5900 Blaster ignition and an MSD 8202 Baster 2 coil. It seems I could use one or the other with no problem, either the MSD ignition with the stock coil or the MSD coil with the stock ignition, but if I had both installed I would get a stumble on accelerating from a dead stop.
From this behavior I deduced that, for some reason, the problem was being caused by too much ignition voltage. To test out that theory I installed a 1 ohm ballast resistor in line with the +12 volts going to the coil. Voila, the problem vanished and I was back to strong, smooth acceleration from a dead stop. So then I tried a 1/2 ohm ballast resistor and the stumble returned, but not as bad, so I went back to the
1 ohm resistor.The stock coil has about a 1.5 ohm primary and the MSD coil has a .7 ohm or so primary. I don't know what impact this has on the situation but it's info that I have and I figured I might as well throw it in if I am going to all the trouble of posting this and you are going to all the trouble of reading it.
Now we get to meat of the my puzzlement. The ignition wires that I have on the engine measure about 3000 ohms per foot. For about $45 I can buy some MSD Street Fire wires that are only 500 ohms per foot. I know a bit about electricity, but not enough to know whether or not these wires would enable me to run the MSD ignition and coil without the ballast resistor. After all, the point of an MSD ignition upgrade is to get longer stronger spark to the plug.
I don't have a clue as to why the engine stumbles with both the MSD ignition and coil installed. From the symptoms it seems to me that it must be because of too much voltage at the coil tower, but why that might be causing the problem is beyond me.
Could it be because the high voltage is leaking out to ground somewhere on the way to the plugs? I checked the engine at idle in a dark area at night and saw no evidence of arcing. Could the high resistance wires be the cause? If so, what is the rationale? I can't think of one.
Well that's it. At present, I am more than happy with the ballast resistors. The truck runs great. Just curious as hell as to what might be going on.
Jack