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

Repeating a previously-reported real similar event-- over a year ago on the 6-Volt system of our ’55 C-300. Much loss of power. Carbs, plugs, ignition components, even valve springs checked out or replaced—nothing helped. Finally, the wire between the coil and the distributor was checked and found to be a high-resistance component—probably due to frayed or broken strands of copper. The simple little wire was replaced and the problem went away. Who’d a thunk it? And, I used to diagnose this problem on stovebolt Chebbies in the ‘50’s where that wire would occasionally fray or break from vibration, oil and heat.

I don’t know what the current draw of the ignition system is at speed and load but all wires and connections need to be in top shape. A friend had his C or D just die on the road and could not get started. Careful study revealed a loose connection on one of the tiny wires connecting the dual points. The wire was still stuck behind the screw but the screw was just loose enough to create an intermittent situation. The connection looked OK but needed to be physically checked with just the right ignition-grade screwdriver—a really challenging job on hemi’s.

Both experiences involved wasted expenditures. I hope sharing them might be of some help.

C300K’ly,

Rich Barber

Brentwood, CA (NOT OJ’s home town)

From: Chrysler300@xxxxxxxxxxxxxxx [mailto:Chrysler300@xxxxxxxxxxxxxxx] On Behalf Of Michael Moore mmoore8425@xxxxxxx [Chrysler300]
Sent: Friday, March 04, 2016 6:55 AM
To: Mike Moore <mmoore8425@xxxxxxx>
Cc: Chrysler300@xxxxxxxxxxxxxxx
Subject: [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
300H

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Posted by: "Rich Barber" <c300@xxxxxxx>

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