[Chrysler300] Surprising source of miss in 300 ?
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[Chrysler300] Surprising source of miss in 300 ?

I have been trying to eliminate a miss in my 300H. 

In the ongoing effort, I have replaced the damper, installed a Philbin rebuilt distributor, new plug wires, new plugs, carbs “restored”, coil replaced etc.  with no improvement. Even 108 octane gasoline hasn’t helped.

 I made arrangements for a visit to a  great shop with a Sun engine analyzer (equivalent) , but I had to get it running reliably enough to get down there, and it now ran worse each time I started it. 

 Judging the problem to be ignition related versus carbs, I decided to strip and replace the entire ignition apparatus from ballast resistor through plugs.  I  ordered  NOS Champion J-12Y plugs (which have always worked well for me), a new set of ignition cables (which are the best I have seen), a new coil, correct Mopar points,  and new capacitor. 

I began with a new correct ballast resistor and noticed  the old ballast resistor ceramic  wire wound resistor inside was broken into two pieces. As I  hadn’t disassembled the rest of the system, I started the car with the new ballast resistor with no improvement, so I incorrectly dismissed that as the source of my miss. 

While waiting for my original new parts to arrive, and after doing a thorough (165# on all 8) compression check   (because all the plugs were out, front wheels were off and access was so easy),  I disassembled the points from the distributor last night. 

I found them badly burned! Aha!
 My earlier distributor trouble shooting was to check only the dwell angle since it had recently been rebuilt. I noted the dwell angle had increased to 45 degrees since I installed the distributor when it came back from Philbin.  

I now believe what happened was that the ballast resistor failed sometime in past years, allowing the points to burn because of the higher than specified voltage on the coil. In recent years I haven’t driven the car much, but have changed the points entirely too often and haven’t noticed it too much because although it might be only 1500 miles,  it may have been 3 years. I am certainly anxious to get it back together.

Thanks for all the help on line and off.
Mike Moore

Posted by: Michael Moore <mmoore8425@xxxxxxx>

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